Hollow porous microspheres as substrates and containers for catalyst

ABSTRACT

Hollow porous microspheres are used as substrates and containers for catalyst to make microsphere catalysts. 
     The hollow porous microspheres are made from dispersed particle compositions. The microspheres have a single central cavity, have substantially uniform diameters and substantially uniform wall thickness and the walls of the microspheres have substantially uniform void content, i.e., interconnecting voids, and have substantially uniform distribution of interconnecting voids. The interconnecting voids in the walls of the microspheres are continuous and extend from the outer wall surface of the microsphere to the inner wall surface of the microsphere. 
     The microsphere catalysts are prepared by coating or impregnating the hollow porous microspheres with a catalyst or by applying a catalyst support to the microspheres and then coating or impregnating the microspheres and catalyst support with a catalyst. 
     The microsphere catalyst can also be prepared by filling the hollow porous microspheres with a catalyst or catalyst and catalyst support. 
     The microsphere catalyst can be treated to immobilize the catalyst and can be treated to provide the microsphere with a selective membrane. The microsphere catalyst can be used for a wide variety of catalyst reactions.

This application is a continuation of application Ser. No. 886,742 filedJuly 18, 1986, abandoned, which is a divisional of application Ser. No.711,951 filed Mar. 14, 1986, U.S. Pat. No. 4,637,990, which is acontinuation-in-part of Ser. No. 639,126 filed Aug. 9, 1984, U.S. Pat.No. 4,671,909, and a continuation-in-part of Ser. No. 657,090 filed Oct.3, 1984, said Ser. No. 639,126 is a continuation-in-part of Ser. No.428,923 filed Sept. 30, 1982, U.S. Pat. No. 4,548,196, which is acontinuation of Ser. No. 103,113 filed Dec. 13, 1979, abandoned, whichis a division of Ser. No. 059,296 filed July 20, 1979, abandoned, whichis a continuation-in-part of Ser. No. 937,123 filed Aug. 28, 1978,abandoned, and Ser. No. 994,643 filed Sept. 21, 1978, abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to novel hollow porous microspheres used assubstrates for catalyst and used as containers for catalyst to carry outa wide variety of catalyst reactions.

2. Prior Applications

The present application is a continuation-in-part of my copendingapplication Ser. No. 639,126 filed Aug. 9, 1984 and my copendingapplication Ser. No. 657,090 filed Oct. 3, 1984.

SUMMARY OF THE INVENTION

The present invention relates to microsphere catalysts made from hollowporous microspheres where the hollow porous microspheres are used assubstrates and containers for catalysts.

The term microsphere catalyst as used herein is broadly defined toinclude a hollow porous microsphere which has been treated to coat orimpregnate the walls of the microsphere with a catalyst or a catalystand a catalyst support, or which has encapsulated or contained withinthe hollow central cavity of the microsphere a catalyst and/or catalystsupport.

The hollow porous microspheres used as substrates and/or containers inaccordance with the present invention are substantially spherical inshape, have substantially uniform diameters and have substantiallyuniform wall thickness and a single central cavity. The microsphereshave interconnecting voids in the walls of the microspheres which resultin the porous characteristics of the mirospheres. The microspheres haveuniform size and shape, uniform diameters, uniform wall thickness,uniform void content and uniform distribution of voids in the walls andhigh strength.

The walls of the hollow porous microspheres are free of latent solid orliquid blowing gas materials, and are substantially free of relativelythinned wall portions or sections and bubbles.

The hollow porous microspheres can be made from ceramic, glass, metal,metal glass and plastic particles, and mixtures thereof. The materialsfrom which the microspheres are made can be selected to have catalyticactivity as well as to provide good substrates for catalyst deposited onor contained in the hollow microspheres.

The microsphere catalyst of the present invention can be prepared by thebelow procedures.

(a) The microsphere catalyst can be prepared by coating or impregnatingthe hollow porous microspheres with a catalyst.

(b) The microsphere catalyst can be prepared by applying a catalystsupport to hollow porous microspheres and then coating or impregnatingthe microspheres and catalyst support with the catalyst.

(c) The microsphere catalyst can be prepared by filling the microsphereswith catalyst or catalyst and catalyst support.

(d) The microsphere catalyst can be prepared by coating or impregnatinga support with a catalyst and filling the microspheres with the catalystcoated on the support.

The hollow porous microspheres of the present invention can be employedto encapsulate liquids, slurries or sol dispersions of catalyst,catalyst supports or catalyst precursors which can be caused to bedeposited in the central cavity of the microspheres by hydrostaticpressure, by suction, or by centrifugation.

The microsphere catalyst prepared by the above procedures can be treatedto immobilize the catalyst contained in the microsphere.

The immobilizing means can be a selective membrane which reduces thepore size of the hollow porous microspheres, such that the catalystcontained within the microsphere is prevented from escaping from themicrosphere through the pores and entrance means, while only specificliquids, gases and/or organic molecules of predetermined molecular sizecan enter or leave the microsphere through the selective membrane.

The microsphere catalyst prepared by the above procedures can be treatedto coat or impregnate the microsphere walls with an inorganic selectivemembrane or for low temperature reactions an organic selectivesemipermeable membrane to protect the catalyst and to provide a means tocarry out selective chemical reactions.

The selective membrane can be used to protect the catalyst from damageor contamination. The selective membrane can also be used to control theselectivity of the catalyst reaction and thereby, for example, combinethe processes of membrane selection and separation and catalyticactivity.

The present invention also relates to methods for coating orimpregnating and/or filling hollow porous microspheres with catalystand/or catalyst supports to prepare improved microsphere catalysts. Thehollow porous microspheres can be used as substrates or containers for awide variety of catalyst and catalyst supports.

The porous wall of the hollow microsphere include entrance means throughwhich catalyst and/or catalyst supports are introduced into the hollowinterior or single central cavity of the microsphere. The porous wallcan subsequently be treated to include means for immobilizing thecatalyst within the hollow interior of the microsphere.

In an embodiment of the invention catalyst is introduced into the singlecentral cavity of the microsphere. According to this embodiment, hollowporous microspheres each having entrance means in its porous wall whichentrance means are large enough for the catalyst to pass through intothe hollow interior are used. A slurry is brought into contact with themicrospheres and sufficient pressure is applied for the slurry to passthrough the entrance means into the hollow interior of the microsphere.

The term entrance means as used herein include microsphere pores, macropores and micro pores. The microsphere pores, i.e. the interconnectingvoids in the walls of the microspheres, are those obtained duringformation of the microspheres and sintering of the dispersed particlecompositions. The macro pores are those obtained by melting, vaporizingor decomposing macro particles contained in the walls of themicrospheres. The micro pores are those obtained by treating themicrospheres with a sol dispersion or sol gel to deposit the soldispersion or sol gel in the microsphere pores and/or macro pores andheating to elevated temperatures to form from the sol dispersion or solgel the micro pores in the interconnecting voids and macro pores in themicrosphere walls.

The microsphere catalyst can be used to carry out a wide variety ofcatalyst reactions. The term catalyst reactions is defined as anychemical reaction carried out effected by a catalyst. The term catalystreactions includes petroleum refining processes, chemical processes andemision control processes. The term catalyst reaction is to be given asbroad a meaning as possible consistent with the requirement that itinvolves the use of at least one reactant which is modified, converted,altered, or otherwise reacted, more or less specifically, through theassistance of the catalyst in order to manufacture or modify aparticular substance. Thus, catalyst reactions encompass such diversetechnologies as petroleum refining process, e.g. catalytic cracking,alkylation, hydrotreating, hydrocracking and catalytic reforming;chemical processes, e.g. polymerization, organic synthesis,ammoxidation, oxidation and oxchlorination, ammonia and methanolsynthesis; and emission control, e.g. automobile emission control andemission control of effluents from incinerators, power generationplants, ovens, wood stoves and acid plants. The term catalyst reactions,as used herein, is intended to exclude the biotech reactions, e.g.biological processes disclosed and claimed in applicant's copendingapplication Ser. No. 657,090 filed Oct. 3, 1984.

PRIOR ART

In recent years, there have been many attempts to improve catalystproperties by using hollow porous microspheres as catalyst substratesand as containers for catalyst. Though there are known methods forproducing hollow microspheres the known methods suffer one or moreshortcomings including producing very small microspheres, microspheresof random wall size and diameter distribution, microspheres whichcontain latent liquid, solid or gas blowing agents, and microsphereswhich have thin wall sections or walls having small gas bubblesdissolved or trapped in the walls. See, for example, Sowman U.S. Pat.No. 4,349,456 (sol gel process), and De Vos et al U.S. Pat. No.4,059,423 (latent blowing gas process). The shortcomings present in theprior art microspheres made it difficult to obtain microspheres of thedesired porosity and strength and to obtain catalyst of controlled andpredictable activity and made it difficult to control the desiredcatalyst reactions.

Prior to the time applicant made the present invention there was noknown simple economical method of producing for use as catalystsubstrate or containers for catalyst relatively large porousmicrospheres where the microspheres were substantially spherical, ofsubstantially uniform diameter, uniform wall thickness, uniform voidcontent and uniform void distribution and intercommunication of thevoids in the walls and uniform strength and where the microspheres couldbe produced at about ambient temperatures. Prior to the time applicantmade the present invention there was no ready means for encapsulatingcatalyst, e.g. solid particulate catalyst in a rigid hollow microsphereor means for immobilizing catalyst in a rigid hollow microsphere, e.g.by use of an immobilizing membrane.

Further, the conventionally produced catalyst, e.g. catalyst withbinders, catalyst without binders and molecular sieve catalyst tendduring use to attrite with the formation of small particles and/orfines. The small particles and/or fines in some reactions elutriate andare loss to the reaction and may cause pollution problems and/orcontamination of the desired products. The small particles formed byattrition or the particles that are the small particles of wide ornarrow particle size distribution of catalyst, tend to cause packing ina catalyst bed. The packing of the catalyst bed can cause an increasepressure drop across the catalyst bed and can cause channeling of thereactant in the catalyst bed which results in reduced contact betweenthe catalyst and reactant.

Where binder materials are required to bind the catalyst particles toform the desired size and shape of catalyst pellet, the binder tends toreduce the diffusion rate at which the reactant can reach the catalystand reduces the rate of the reaction. The use of binders also reducesthe surface area of the catalyst available to the reactant.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide improved microspherecatalysts using hollow porous microspheres as catalyst substrates andcontainers for catalysts.

It is another object of the invention to prepare microsphere catalystsfrom hollow porous microspheres, which microspheres have a singlecentral cavity, have substantially uniform diameters and substantiallyuniform wall thickness, where the walls of the microspheres havesubstantially uniform void content and substantially uniformdistribution of interconnecting voids.

It is another object of the invention to prepare microsphere catalystsby coating or impregnating hollow porous microspheres with a catalyst orby applying a catalyst support to the microspheres and then coating orimpregnating the microspheres and catalyst support with a catalyst.

It is another object of the invention to prepare microsphere catalystsby filling the hollow porous microspheres with a catalyst or with acatalyst and catalyst support.

It is another object of the invention to immobilize the catalystcontained in the microspheres by treating the microspheres containingthe catalyst to agglomerate the catalysts to a sufficiently large sizesuch that the catalysts do not flow out of the catalyst entrance means.

It is another object of the invention to immobilize the catalystcontained in the microspheres by treating the microspheres containingthe catalyst to provide the microspheres with an inorganic or organicmembrane such that the catalyst is immobilized and protected.

It is another object of the invention to provide the microspherecatalysts with an organic selective membrane or an organic selectivemembrane such that selective chemical reactions can be carried out.

It is another object of the invention to provide structural support forcatalysts without significantly diminishing the diffusion rates ofreactant gases or liquids through the microsphere substrate ormicrosphere container and into and out of contact with the catalystssuch that the high reaction rates can be obtained and maintained.

It is another object of the present invention to provide extremelyfinely divided substrates within the microspheres for deposition ofcatalyst, which substrates would be too weak in a reactor environment.

It is another object of the present invention to allow extremely smallsize catalyst particles contained within thbe microspheres to be used ina reactor environment which otherwise would elutriate and carry awaysuch small catalyst particles.

It is another object of the present invention to provide microspherecatalyst for carrying out a wide variety of catalyst reactions.

It is another object of the invention to provide microsphere catalystsfor use in fixed bed, moving bed, fluidized bed, batch, continuous orsemi-continuous catalyst reactions.

These and other objects of the invention will become apparent as thedescription proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings and photographs illustrate exemplary forms of thepresent invention for making microsphere catalysts from hollow porousmicrospheres and illustrate hollow microsphere catalysts that areobtained.

The FIG. 1 of the drawings is an enlarged cross-sectional view of ahollow porous microsphere useful as a catalyst substrate and catalystcontainer.

The FIG. 2 is a cross-sectional view of the microsphere similar to FIG.1 showing catalyst deposited on the inner wall surface of themicrosphere wall.

The FIG. 3 of the drawings is an enlarged cross-sectional view of ahollow porous microsphere including multiplicity of macro poresextending through the microsphere walls and showing catalyst depositedon the inner wall surface of the microsphere wall.

The FIG. 4 is a cross-sectional view of the microsphere similar to FIG.3 showing the single central cavity filled with catalyst and the macropores sealed with a selective membrane.

The FIG. 5 is an enlarged cross-sectional view of a section of the wallof a hollow microsphere of FIG. 2 which has been impregnated with acatalyst solution and heated to remove the liquid phase of the solutionand to deposit catalyst on the inner and outer wall surfaces and in theinner connecting voids in the wall.

The FIG. 6 is a cross-sectional view of a section of the wall of amicrosphere similar to FIG. 5 which has been treated with a soldispersion and again heated at elevated temperature to deposit solidparticles from the sol dispersion. The solid particles form a latticework of the particles in the inner connecting voids in the wall toreduce the pore size, i.e., to produce micro pores, which micro porescan provide support for a catalyst to be deposited on or impregnated inor otherwise placed in the micro pores or which can form an inorganicselective membrane.

The FIG. 7 is a cross-sectional view of a section of the wall of amicrosphere similar to FIG. 5 in which the pores in the wall of thehollow microsphere have been sealed with an organic selectivesemipermeable membrane to protect a contained catalyst and to make thecatalytic reaction selective.

The FIG. 8 is a microphotograph (900×) of a top view of a portion of amicrosphere wall similar to FIG. 3 showing a macro pore therein.

The FIG. 9 is a schematic illustration of a bed of microspheres whichhave macro pores and which are partially filled with a finely dividedcatalyst.

FIG. 10 is a photograph (900×) showing a section of the thin wall and asection of the inner wall surface of an alumina particle microsphere onwhich inner wall surface there has been deposited finely dividedcatalyst.

FIG. 11 is a photograph (900×) showing a cross section of the thin walland the inner wall surface of a section of an alumina particlemicrosphere.

THE ADVANTAGES

The present invention overcomes many of the problems associated withprior attempts to produce catalysts from hollow microspheres. Thepresent invention allows the production of improved microspherecatalysts from rigid hollow porous microspheres, wherein themicrospheres have predetermined characteristics of uniform diameter,uniform wall thickness and uniform void content, uniform voiddistribution and void intercommunication in the walls and high strengthsuch that hollow porous microsphere catalysts can be designed,manufactured and tailor made to suit a particular desired process use.The diameter, wall thickness, void content, void distribution and voidintercommunication in the walls, strength and catalytic properties ofthe hollow porous microspheres can be determined by carefully selectingthe catalysts, catalyst supports, the constituents of the dispersedparticle composition, particularly the dispersed solid particles, thesize of the dispersed solid particles and the volume percent solids ofthe dispersed particles, i.e., liquid/solids, composition.

The present invention allows a wide range of selection of particles toform the hollow porous microspheres and a wide range of selection ofcatalysts and catalyst supports to form the microsphere catalysts.

The present invention provides a practical and economical means by whichcatalysts can be made using hollow porous microspheres having uniformdiameters and uniform thin walls of high strength as the catalystsubstrates and/or a containers for the catalysts. The present inventionallows rapid encapsulation, i.e. filling of the microspheres withrelatively large particle size catalysts through macro pore entrancemeans. The present invention provides for the production of catalystsfrom hollow porous microspheres at economical prices and in largequantities.

The present invention, as compared to the prior art process (De Vos U.S.Pat. No. 4,059,423) for producing a hollow microspheres using a latentliquid or solid blowing agent to produce the hollow microspheres,produces catalyst from uniform size spheres as compared to spheres ofrandom wall size and diameter distribution, and produces catalysts frommicrospheres the walls of which are of uniform thickness, are free ofthin walled portions, trapped bubbles or gases, or trapped latentblowing agents which weaken the microsphere walls.

The present invention, as compared to the prior art sol gel microcapsuleprocess (Sowman U.S. Pat. No. 4,349,456), produces large uniform sizespheres for use as catalyst substrates and catalyst containers withuniform thin walls. The Sowman sol gel process produces small sphereswhich are of random size distribution and which spheres have thin andweakened wall portions.

An additional advantage of the microsphere catalysts of the presentinvention is that the catalysts do not require a binder material and areno longer diffusion limited by the effect of the binder.

A further advantage of the microsphere catalysts of the presentinvention is that the pressure drop across a catalyst bed issubstantially reduced by the avoidance of attrition formation of smallcatalyst particles and packing of the catalyst bed.

A still further advantage of the microsphere catalysts of the presentinvention is that improved catalyst-reactant contact is maintained bythe avoidance of channeling of the reactant.

The microsphere catalysts can provide high flux rates of reactants,while still providing greater overall strength. The microspherecatalysts of the present invention in some applications can withstandtwo point pressures up to at least about 200 psia, for example, 500psia. In view of the high wall strength, the microsphere catalysts aremuch more easily handleable and transferrable and can be used in fixedbed processes at high packing densities, for example, bed heights of upto 30 feet or more, in moving bed processes, and in fluidized bedprocesses wherein the microsphere to microsphere contact and microsphereto reactor wall contact impacts do not cause structural damage to themicrosphere or to the catalyst. Further, the generally low density andmass of the microsphere catalysts contributes to this advantage and alsoreduces the shear and impact forces which could be harmful to themicrosphere catalysts.

Because of the relatively low cost of the microspheres the catalyst canbe discarded periodically for short life time catalyst. The microspherecatalyst can also be recycled for regeneration of the catalyst.

In addition, the microspheres of the present invention are more uniformin wall size diameter size than the prior art microspheres. Further, amuch wider range of diameters and wall thicknesses are available for themicrospheres than those used in the conventional catalyst processes.Therefore, control of process parameters, e.g. mass flow rates, fluiddynamics, heat transfer, etc., is greatly simplified.

Because the microspheres are hollow and have porous walls, they willgenerally have bulk densities which are significantly lower than thedensity of the solid particles forming the microsphere walls. Themicrospheres when filled with catalyst can approximate the density ofthe liquid reaction mediums used in some catalyst processes. Themicrospheres, i.e. microsphere catalysts, can accordingly be more easilysuspended in liquid reaction mediums or other liquid mediums, e.g. awaste stream, etc., used in the catalyst process. Further, because ofthe microsphere catalysts relatively low densities they are also moreeasily suspended in vapor phase or gaseous reaction mediums.

The relatively low densities of the microsphere catalysts of the presentinvention provide the highly important advantages of: less mechanicalenergy is required to mix or stir suspensions of the microspherecatalysts in catalytic reactions thereby lower overall costs forcarrying out the reactions. The lower microsphere catalysts densitiesreduces the impact forces or collision pressures ofparticle-to-particle, i.e. microsphere catalyst-to-microsphere catalyst,collisions, thereby reducing the likelihood of damage to the catalystsand/or to the microsphere walls, and reducing the likelihood of damageor shearing stresses to immobilizing means or selective membranes. Inaddition, the low microsphere catalyst densities reduces the timerequired to heat the catalyst to operating temperatures.

Still, another advantage of the microsphere catalysts of this inventionis that the microsphere containers, while non-deformable underconditions of use in the catalyst reaction processes, can be brokenwhere necessary or desired for recovery of the catalysts.

Additional advantages occur in the microsphere catalysts where theprocesses are inhibited by intracrystalline or intercrystallinediffusional resistance, elutriation of fine particles, and problems ofgross handling and efficiency of contacting.

A variation, in which colloidal micro-solids are used to partially blockthe regular microsphere pores, allows increased catalyst surface areaand a protective selective membrane for the contained catalyst.

An added advantage of the present invention is the preparation ofbinderless pellets, with or without a protective inorganic or organicselective permeable membranes.

These and oter advantages of the present invention will become evidentby the description of the invention that follows.

DETAILED DESCUSSION OF THE DRAWINGS

The invention will be described with reference to the accompanyingFigures of the drawings wherein like numbers designate like partsthroughout the several views.

FIG. 1 of the drawings is an enlarged cross-sectional view of a hollowporous microsphere 41 used as a catalyst substrate or catalyst containerin accordance with the present invention. The microsphere illustratedshows dispersed particles 42, interconnecting voids 46 (see also FIG. 5)and a single central cavity 50.

The FIG. 2 is a cross-sectional view of the microsphere similar to FIG.1 showing catalyst 51 deposited on the inner wall surface 52 of themicrosphere wall. The catalyst can be deposited from a solutioncontaining the catalyst or by impregnation of the hollow microspherewith the solution and drying to deposit the catalyst. The catalyst 51 isalso deposited in the interconnecting voids or channels 46, and on theouter surface of the microsphere wall. The catalyst in theinterconnecting voids and on the outer wall surface are not shown, seehowever FIG. 5 below.

The FIG. 3 of the drawings is an enlarged cross-sectional view of ahollow porous microspheres 41 including a multiplicity of macro pores 44of a predetermined size extending through the microsphere wall andshowing catalyst 51 deposited on the inner wall surface 52 of themicrosphere wall. The FIG. 3 also shows dispersed particles 42 andinterconnecting voids 46. The catalyst 51 can be deposited from asolution containing the catalyst or by impregnation of the hollowmicrosphere with the solution and drying to deposit the catalyst. Thecatalyst 51 is also deposited in the interconnecting voids or channels46, and on the outer surface of the microsphere wall. The catalyst inthe interconnecting voids 46 and outer wall surface, as in FIG. 2, arenot shown, see however FIG. 5 below. The macro pores 44 allow easycommunication of the reactant into and out of the single central cavity50 of the microsphere such that efficient contact of the reactant withthe catalyst is achieved.

The FIG. 4 is a cross-sectional view of the microsphere similar to FIG.3 showing the single central cavity 50 filled with a solid particulatecatalyst 54 and showing macro pores 44 that are sealed with an inorganicpermeable membrane 53. The FIG. 4 of the drawing shows macro pore 44entrance means, e.g. openings or passageways of larger dimensions thanthe largest microsphere pores 46, 47 and 48 (FIG. 5), that are providedto ensure that the catalyst 54 suspended, e.g. in a slurry or soldispersion will readily pass through the entrance means 44 which extendthrough the wall 45 of the microsphere 41 into the hollow central cavity50 of the microsphere. The relatively large macro pore entrance means inthe walls of the microsphere, are at least twice as large as the maximummicrosphere pore size and preferably at least twice as large as thecatalyst particles 54. The term entrance means broadly includes themicrosphere pores, the interconnecting voids and the macro pores.However, even with small dimensioned catalyst particles, it is preferredto include macropores 44 in the microsphere wall to facilitate andexpedite the process of encapsulating the catalyst or filling themicrospheres with catalyst and to allow good access of the reactants tothe catalyst contained in the microspheres.

The FIGS. 5, 6 and 7 show enlarged detailed cross-sectional views of asection of the wall of a hollow porous microsphere similar to FIGS. 2 or3 used in accordance with the present invention to make an improvedcatalyst. The FIGS. 5, 6 and 7 show pores 47 at the outer wall surfaceof the microsphere which pores extend by interconnecting voids 46through the wall 45 of the microsphere to the inner wall surface pore 48of the microsphere.

As can be seen from FIGS. 5, 6 and 7 the sintered together particles 42forming the solid porous wall 45 of the microsphere 41 define, withinthe wall, interconnecting voids or channels 46. For simplicity ofillustration, the particle-to-particle contact of the sintered togetherparticles is not shown. The interconnecting voids 46 are continuous andextend, from the pore opening 47 at the outer wall surface to the poreor opening 48 at the inner wall surface. The interconnecting voids 46provide paths or passageways for transporting gases, liquids and veryfinely divided, e.g. submicron, dispersed particles from the exterior ofthe microsphere to the interior single central cavity 50 of themicrosphere 41.

The FIG. 5 is an enlarged cross-sectional view of a section of the wallof a hollow microsphere of FIG. 2 or 3 which has been impregnated with acatalyst solution and heated to remove the liquid phase of the solutionand to deposit catalyst on the inner and outer wall surfaces and in theinner connecting voids 46 in the wall. The FIG. 5 shows catalyst 51deposited on the outer wall surface 45 of the microsphere, on the wallsor surfaces of the interconnecting voids 46 and on the inner wallsurface 52 of the microsphere.

The FIG. 6 is a cross-sectional view of a section of the wall of amicrosphere similar to FIG. 5 which has been treated with a soldispersion and heated at elevated temperature to deposit solid particlesfrom the sol dispersion. The microspheres can be treated with a soldispersion or a sol gel, e.g., an alumina or silica sol gel, or otherdispersions of charged or uncharged colloidal particles and heated atelevated temperature to deposit in the interconnecting voids 46 and onthe surfaces of the particles that form the interconnecting voids of themicrosphere wall small solid particles 49, e.g., alumina or silicaparticles. The deposited alumina or silica particles can form a catalystsupport and/or an immobilizing or a selective membrane. The soldispersion or sol gel composition can be deposited in a layer in theouter portion of the microsphere wall, in the center portion, in theinner portion of the microsphere wall or throughout the microspherewall. The solid particles from the sol dispersion or sol gel aredeposited and adhere to the surfaces of the particles that form theinterconnecting voids 46, and the solid particles from the soldispersion link-up and form in the interconnecting voids a porouslattice work of linked-up deposited sol or sol gel particles.

The porous lattice work of solid particles from, e.g., the soldispersion or sol gel deposited in the interconnecting voids and on thesurface of the particles that form the voids 46 serves to reduce thevoid content, i.e., the volume percent voids and the pore size of thevoids in the microsphere wall, i.e., form micro pores, when a controlledsmaller pore size is desired. The reduction of the pore size and thevoid content at the same time increase the surface area of support inthe pores in those embodiments in which it is desired to deposit,impregnate or otherwise place a catalyst in the interconnecting voidsand/or on the outer pore area of the microsphere wall.

In a preferred embodiment of the invention, the catalyst or a selectivemembrane is impregnated or deposited within the microsphere wall tostrengthen the adhesion of the catalyst or selective membrane to thehollow microsphere wall and avoid lifting off of the catalyst and/orselective membrane during catalytic processes or regeneration cycles.

The FIG. 7 is a cross-sectional view of a section of the wall of amicrosphere similar to FIG. 5 in which the pores in the wall of thehollow microsphere have been impregnated and sealed with an organicselective semipermeable membrane 53 to protect a contained catalyst andto make the catalytic reaction selective. The organic semipermeablemembrane 50 is impregnated, deposited or otherwise placed in themicrosphere wall through surface pores 47 and into voids orinterconnecting channels 46, closing pores 47 and forming adiscontinuous thin film 50 in the wall of the hollow microsphere.

The FIG. 8 is a micro photograph (900× magnification) of a top view of aportion of the microsphere wall showing a macro pore therein. The FIG. 8shows a top view of a portion of a microsphere wall 40 micron thickafter decomposition of an acrylic macro particle of about 50 micronsdiameter. The sintered solid particles forming the microsphere wall arealumina (Al₂ O₃) particles having a particle size of about 1 to 3microns. The microsphere is about 4000 microns in diameter and is madefrom alumina particles.

As can be seen from the micro photograph of FIG. 8, the perimeter of themacro pore is generally free of sharp or jagged protrusions which couldresult from extension into the macro pore of portions of one or more ofthe finely divided solid wall-forming particles since any such sharp orjagged protruding solid particles will tend to be smoothed by thesubsequent sintered step. However, it is possible to even furthersmoothen the surface of the macro pore by using as the macro particles amaterial, such as glass and metals, which at least partially soften andmelt, rather than decompose, at the operating temperature. In such case,when the microsphere is heated, at least a portion of the macro particlewill diffuse and penetrate into and between the dispersed solidparticles surrounding and coating the macro particle thereby assuringleaving behind a smooth macro pore surface (periphery). Furthermore, itis possible to select mutually reactive materials for the finely dividedsolid particles and the macro particles, for example, alumina solidparticles and glass macro particles, which will react to form aluminasilicate, at or below the sintering temperature, thereby furtherstrengthening, as well as smoothing, the macro pore surface.

The FIG. 9 of the drawings is a schematic illustration of a bed ofmicrospheres 41 which have macro pores 44 and which are partially filledwith a finely divided catalyst 54. Gas or liquid feed reactant medium 61enter microspheres 41 through macro pores 44, contact catalyst 54 incentral cavity 50 and react to form the desired product and by-products62. The product and by-products together with an unreacted feed 63 exitthe central cavity 50 by way of macro pores 44 to go to furtherprocessing. Each microsphere 41 with its catalyst 54 and central cavity50 comprises an individual small reactor.

The FIG. 10 is a photograph (900×) showing a section of the thin walland a section of the inner wall surface of a hollow porous aluminaparticle microsphere and showing finely divided silica catalystdeposited on the inner wall surface of the microsphere wall. The silicacatalyst was deposited from an aqueous sol consisting of colloidalsilica. The microsphere was placed in the sol until saturated with thesol, dried and then heated to deposit the catalyst. The microsphere hasa diameter of 2400 microns and a wall thickness of 30 microns.

The FIG. 11 is a photograph (900×) showing a cross section of the thinwall and the inner wall surface of a hollow porous microsphere made fromalumina particles. The microsphere is about 3000 microns in diameter andhas a wall thickness of 25 microns and 40% void content in the wall.

DESCRIPTION OF HOLLOW POROUS MICROSPHERES

The hollow porous microspheres provide uniformly sized substrates anduniformly sized containers for catalysts. The method for the manufactureof the microspheres and their physical properties and dimensions aredisclosed in and are the subject matter of applicant's copendingapplication Ser. No. 639,126 "Hollow Porous Microspheres and Method andApparatus For Producing Them", filed on Aug. 9, 1984. The entiredisclosure of the copending application is incorporated herein in itsentirety by reference thereto.

The hollow porous microspheres of the present invention can be made fromdispersed particle compositions which comprise dispersed particles, abinder, a film stabilizing agent, a dispersing agent and a continuousliquid phase.

The hollow porous microspheres are made from aqueous or non-aqueoussuspensions or dispersions of finely divided inorganic or organic solidparticles, particularly ceramic, glass, metal, metal glass and plasticparticles, a binder material, a film stabilizing agent, a dispersingagent for the solid particles, and a continuous aqueous or non-aqueousliquid phase. The suspension or dispersion is blown into microspheresusing a coaxial blowing nozzle, the microspheres are heated to evaporatethe solvent and further heated or cooled to harden the microspheres. Thehardened microspheres are then subjected to elevated temperatures todecompose and remove the binder and any residual solvent or low boilingor melting material. The resulting hollow porous microspheres are thenfired at further elevated temperatures to cause the particles to sinterand/or fuse at the points of contact of the particles with each othersuch that the particles coalesce to form a strong rigid network (latticestructure) of the sintered-together particles.

As described in the copending application Ser. No. 639,126, macro porescan be obtained by incorporating in the solid particle suspension ordispersion, prior to the blowing step, a small percentage ofdecomposable particles (macro particles) having a diameter greater thanthe maximum dimension of the microsphere wall, for example, about 1 to1000 microns, preferably 5 to 400 microns, more preferably about 10 to100 microns, especially preferably about 20 to 100 microns. Thesedecomposable macroparticles are confined along with the smallerdispersed solid particles in the wall of the microsphere. However, thedecomposable macro particles are decomposed at the step of decomposingthe organic binder or at the subsequent step of sintering the dispersedparticles depending on the decomposition temperature of the decomposablemacro particles, leaving behind large openings (macro pores), such asshown in FIG. 3. In addition, metal and glass beads or pellets having amelting temperature below the sintering temperature, preferably at least100° C. below the sintering temperature can also be used.

Generally, the material of the dispersed solid particles forming thewalls of the microspheres is not particularly critical so long as it iscompatible with a non-contaminating to the catalyst and not detrimentalto the process, and the ceramic particles, glass particles, metalparticles, metal glass particles, and plastic particles disclosed in theaforementioned patent application Ser. No. 639,126 can be used.

On the other hand, it is often preferred or desirable in certaincatalytic reactions for the catalyst to be deposited and adhered to asubstrate (in the case of the present invention, the substrate being theinner wall surface of the hollow microsphere, and the walls of theinterconnecting voids). In such cases, therefore, the material of thedispersed particles will be selected based on its ability to provide asurface to which the catalyst can be deposited and adhere by physicaland/or chemical bonding. Many materials will naturally meet thisrequirement, although to differing degrees. Furthermore, it is alsoknown in the art to provide chemical treatment to substrates in increasetheir ability to bond to specific catalysts.

The hollow porous microspheres are free of any latent solid or liquidblowing gas materials or latent blowing gases. The walls of the hollowmicrospheres are free or substantially free of any relatively thinnedwall portions or sections, trapped gas bubbles, or sufficient amounts ofdissolved gases to form bubbles.

The term "latent" as applied to latent solid or liquid blowing gasmaterials or latent blowing gases is a recognized term of art. The termlatent in this context refers to blowing agents that are present in oradded to glass, metal and plastic particles. In the prior art processesthe glass, metal and plastic particles containing the "latent blowingagent" are subsequently heated to vaporize and/or expand the latentblowing agent to blow or "puff" the glass, metal or plastic particles toform microspheres.

The hollow porous microspheres, because the walls are substantially freeof any thinned sections, trapped gas bubbles, and/or sufficient amountsof dissolved gases to form trapped bubbles, are substantially strongerthan the hollow microspheres heretofore produced.

The hollow porous microspheres contain a single central cavity, i.e.,the single cavity is free of multiple wall or cellular structures. Thewalls of the hollow porous microspheres are free of bubbles, e.g., foamsections.

The hollow porous microspheres can be made in various diameters and wallthickness, depending upon the desired end use of the microspheres. Themicrospheres can have an outer diameter of 200 to 10,000 microns,preferably 500 to 6000 microns and more preferably 1000 to 4000 microns.The microspheres can have a wall thickness of 1.0 to 1000 microns,preferably 5.0 to 400 microns and more preferably 10 to 100 microns.

When the dispersed particles are sintered, the smaller particles can bedissolved into the larger particles. The sintered particles in thehollow porous microspheres can be generally regular in shape and have asize of 0.1 to 60 microns, preferably 0.5 to 20 microns, and moreprefereably 1 to 10 microns.

In a preferred embodiment the hollow porous microspheres can havediameters of 1200 to 6000 microns and wall thicknesses of 10 to 200microns, and preferably diameters of 2000 to 4000 microns and wallthicknesses of 20 to 100 microns.

The porosity, diameter and wall thickness of the hollow porousmicrospheres will affect the average bulk density of the microspheres.The porous ceramic, glass, metal, metal glass and plastic microspheresprepared in accordance with the invention will have an average bulkdensity of 1 to 150 lb/ft³, (0.020 to 2.4 gm/cc), preferably 2.0 to 60lb/ft³, (0.030 to 1.00 gm/cc), and more preferably 4 to 20 lb/ft³,(0.060 to 0.32 gm/cc).

In certain embodiments of the invention, the ratio of the diameter tothe wall thickness, and the conditions of firing and sintering thehollow microspheres can be selected such that the microspheres areflexible, i.e., can be deformed a slight degree under pressure withoutbreaking.

The preferred embodiment of the invention, particularly with the ceramicmaterials, is to select the ratio of the diameter to wall thickness andthe conditions of firing and sintering the hollow porous microspheressuch that rigid hollow porous microspheres are obtained.

The fired hollow porous microspheres of the present invention can have adistinct advantage of being rigid, strong and capable of supporting asubstantial amount of weight. They can thus be used to make simpleinexpensive catalyst substrates and catalyst containers that can be loadbearing systems for carrying out catalytic reactions.

The hollow porous microsphere containers of this invention, in additionto their uniformity in structure, have the highly advantageouscharacteristic of high mechanical strength due to the sintering togetherof the solid dispersed wall-forming particles. Due to this highmechanical strength, the microsphere resist damage under the conditionsof actual use in catalytic processes. The microspheres have the abilityto withstand the forces exerted by contact with other microspheres orthe walls and surfaces of the process apparatus, as well as hydrostaticforces and pressures encountered in catalytic reaction processes,including fluidized bed, stacked bed, plug flow, and other types ofcatalytic reaction processes, without any significant deformation ofshape and without breakage and, further, without imparting stress forceson the selective membrane or immobilizing means. Preferably the walls ofthe hollow porous microsphere containers are rigid and are capable ofwithstanding two point contact pressure of at least 30 psi (2.1 kg/cm²),preferably from about 50 psi (35 kg/cm²) to about 3000 psi (211 kg/cm²).As used herein "two point contact pressure" is measured with respect toa one-inch square tightly packed monolayer of the microspheres restingon a hard flat surface with a flat mass placed thereon. The weight ofthe mass causing breakage of one or more microspheres divided by onesquare inch is the "two point contact pressure".

The porosity or void content of the walls of the hollow microspheres isdependent upon the volume percent of dispersed solids of the entiredispersed particle composition and the firing and sintering temperature.

The porosity of the walls, i.e., the void content, of the hollow firedmicrospheres can be 5% to 45%, preferably 15% to 35% and more preferably20% to 30% by volume of the microsphere wall.

In an embodiment of the invention the hollow microspheres can besubstantially spherical and can have substantially uniform diameters orthey can have thickened wall portions on opposite sides of themicrospheres. The thickness of the thickened portions depends in part onthe viscosity of the dispersed particle composition, the rate ofhardening, the distance away from the coaxial blowing nozzle when theyharden and the ability of the surface tension properties of thedispersed particle composition to absorb and distribute in the wall ofthe microsphere the portions of the dispersed particle composition thatwould or may form filaments.

The preferred hollow microspheres are the substantially sphericalmicrospheres. However, in some applications, for example, packed bedsystems, the hollow microspheres with the thickened wall portions canalso be used. The thickened wall portions, on the opposite sides of themicrospheres, can be 1.01 to 2.0 times the microsphere wall thickness;can be 1.1 to 1.5 times the microsphere wall thickness; and can be 1.2to 1.3 times the microsphere wall thickness. The cross-section of themicrosphere other than at thickened wall portion section issubstantially spherical and of substantially uniform wall thickness. Allthe microspheres produced under a given set of operating conditions anddispersed particle composition constituents are substantially the samein sphericity, wall thickness, void content and void distribution. Aspecific advantage of the use of the hollow porous microspheres of thepresent invention is that in the production of hollow microspheres, thepreceeding and the following microspheres that are produced aresubstantially the same.

The hollow porous microspheres used to produce the microsphere catalystin accordance with the present invention, depending in part on thedispersed particle size, e.g., 0.1 to 5.0 microns, and dispersedparticle size distribution, volume percent solids used and firingtemperatures, can contain interconnecting voids or channels between thesintered particles in which the distance between particles, can be, forexample, 1 to 5 microns.

The microsphere pores and interconnecting voids or channels will,depending on the size of the dispersed particles and the particle sizedistribution of the dispersed particles and the porosity of themicrosphere walls, can range from about 0.05 to 20 microns, generallyfrom about 0.1 to 10 microns, and more generally from about 0.1 to 5microns. For many catalyst materials having particle sizes of less thanabout 1-2 microns, the pore sizes or at least a substantial portion ofthe pores, will be sufficiently large to permit free passageway of thesecatalysts from the exterior to the interior of the microsphere. However,the pore size may be smaller than or only slightly larger (e.g. up toabout 100% larger) than the maximum dimension of the catalystmaterial--this will generally be the case for many of the catalystmaterials desired to be used. In this case, the microspheres containingmacro pores can be used when it is desired to put the catalyst withinthe central cavity of the microspheres.

In applications in which a hollow porous microsphere is not needed orwanted and/or where it is desired to have maximum wall strength theheating at elevated temperatures can be carried out at temperatures highenough and for a time long enough to melt the dispersed particles, tofuse the pores closed, to fuse the interconnecting voids closed and toremove substantially all of the interconncting void structure from thewalls of the hollow microspheres. The heating at elevated temperaturesis carried out at temperatures high and time long enough enough for theair or other gas in the interconnecting voids to dissolve in the fuseddispersed particles or to form bubbles and migrate to the surfaces ofthe microspheres and out of the walls of the microspheres and to clossoff and seal the interconnecting void structure in the microsphere wall.The treatment step can be carried out in a manner so that it does notcollapse to microsphere wall and the microspheres retain their sphericalshape. In this embodiment the catalyst is deposited on the outer wallsurface of the microsphere.

Alternatively, the microspheres may be treated to have theinterconnecting voids filled and sealed with a dispersion of colloidalsize particles that have a lower melting temperature than the dispersedparticles in the hollow porous microspheres and then heated to fuse thecolloidal size particles to seal the interconncting voids.

Without intending to be limiting but rather to be used as a point ofreference, the Table I below provides exemplary relationships betweenthe outer diameters of the microspheres, microsphere wall thickness,dispersed particle size, and ratio of the microsphere wall thickness tothe outside diameter of the microsphere.

                  TABLE I                                                         ______________________________________                                                  Broad    Preferred More Preferred                                   ______________________________________                                        Diameter     200 to 10,000                                                                            500 to 6000                                                                            1000 to 4000                                 (microns)                                                                     Wall thickness                                                                            1.0 to 1,000                                                                              5.0 to 400                                                                              10 to 100                                   (microns)                                                                     Dispersed  0.005 to 60 0.05 to 20                                                                                0.1 to 10                                  particles                                                                     (microns)                                                                     Macro particles                                                                           1.0 to 1,000                                                                              5.0 to 400                                                                              10 to 100                                   (microns)                                                                     Ratio of wall                                                                             1:4 to 1:500                                                                             1:10 to    1:20 to 1:200                               thickness to Out-      1:300                                                  side microsphere                                                              diameter                                                                      ______________________________________                                    

In certain catalyst applications of the invention, for example, when themicrospheres contain in the single central cavity finely divided carbonparticles, the hollow microspheres can have the dimensions shown belowin Table II.

                  TABLE II                                                        ______________________________________                                                      Preferred More Preferred                                        ______________________________________                                        Diameter (microns)                                                                            1200 to 6000                                                                              2000 to 4000                                      Wall thickness (microns)                                                                       10 to 200   20 to 100                                        Dispersed particles (microns)                                                                  0.05 to 10   0.1 to 5                                        Macro particles (microns)                                                                      10 to 200   20 to 100                                        Ratio of wall thickness to                                                                     1:10 to 1:300                                                                             1:50 to 1:200                                    outside microsphere diameter                                                  ______________________________________                                    

When use as substrates on which a catalyst solution is coated orimpregnated the hollow microspheres can advantageously have diameters of500 to 2000 microns and wall thickness of 50 to 800 microns andpreferrably can have diameters of 600 to 1000 microns and wall thicknessof 100 to 300 microns, respectively.

DISPERSED PARTICLES

The dispersed particles from which the hollow porous microspheres aremade can be selected from a wide varity of materials and the dispersedparticles and can be selected to have catalytic activity. The dispersedparticles can include ceramic materials (including graphite and metaloxides), glasses, metals, metal glasses and plastics, and mixturesthereof.

The dispersed particles can be 0.005 to 60 microns in size, preferably,0.05 to 20 and more preferably 0.1 to 10 microns in size. Generally arelatively narrow particle size distribution of particles are used. Thesmaller particles, e.g., 0.005 to 0.1 micron range size are referred toas colloidal size particles and particles in this size range areavailable in the form of sols or sol gels, or sol or sol gel precursormaterials, and colloidal powders.

When colloidal size particles are used as the dispersed particles or asdispersed particles having catalytic activity the particles can bepurchased as sol dispersions or gels or as colloidal powders or can byconventional means be formed in situ, for example by chemical means fromsol or sol gel precursor materials. A readily available source ofcolloidal size particles are the commercially available sol gelmaterials, colloidal powders, the ball clays and the bentonite clays.Further, there are now available, in concentrations of 10 to 50 weightpercent solids, silica sols and metal oxide sols which can be used asdispersed particles, from the Nalco Company located in Oakbrook, Ill.

MACRO PARTICLES

Though strong hollow microspheres and hollow porous microspheres can beobtained from the dispersed particle compositions, it has been difficultto obtain uniform size openings or pore openings on the outer and innermicrosphere wall surfaces. In accordance with a preferred embodiment ofthe invention macro pore openings of predetermined uniform and precisesize can be obtained. This is done during the manufacture of the hollowporous microspheres by uniformly mixing with the dispersed particlecomposition uniform size macro particles which consist of combustible,vaporizable or meltable materials that will burn or decompose andvaporize or melt at temperatures above the blowing temperatures andbelow the temperatures at which the hollow microspheres are fired andsintered.

In order to obtain the desired size macro pores there is added to thedispersed particle composition and distributed throughout thecomposition a small proportion of combustible, vaporizable or meltablemacro particles. The combustible, vaporizable or meltable particles areselected so that they are burned, vaporize or melt at temperatures belowthe melting temperatures of the dispersed solid particles, but attemperatures above the temperatures at which the microspheres are blown.The size of the combustible, vaporizable or meltable macro particles isselected such that they are about the same size or slightly larger insize than the wall thickness of the hollow microsphere being blown. Inmaking microspheres with macro pores when the microspheres are heatedand fired at elevated temperatures to sinter the dispersed particles,the macro pores are obtained which extend completely through the wallsof the hollow microspheres.

The macro particles are selected to be of uniform size and generallyspherically or spheroid in shape with preferably smooth wall surfaces.The particles are generally solid and made from combustible,decomposable, vaporizable or meltable materials. The meltable materialswhen heated will melt and spread to the adjacent particles. The macroparticle material is selected such that it remains solid at the blowingand microsphere hardening temperatures and is removed at temperaturesbelow the temperatures at which the firing and sintering step is carriedout. Suitable materials for use as macro particles are carbon,naphthalene, anthracene, camphor, polyformaldehyde resins, andpolyethylene, polypropylene and nylon beads or pellets. Various organicpolymeric materials that meet the above criteria can also be used. Inaddition, relatively low melting temperature metals and glasses can beused as the macro particles.

The macro particle size is selected to be about the same or slightlylarger in size than the thickness of the wall of the microsphere inwhich it is to create uniform size macro pores. Thus in microsphereshaving wall thickness of for example 10 to 200 microns, the macroparticles would be about 14 to 280 microns in size, e.g., somewhatlarger than the wall thickness. The diameter of the macro pore can ofcourse be made larger than the thickness of the microsphere wall if suchis desired.

The amount of the decomposable particles incorporated in the suspensionor dispersion is not particularly critical insofar as the amount issufficiently high so that all of the formed porous hollow microspherescontain at least one, preferably at least 5, and especially preferablyat least about 10 to 20 decomposable particles in their walls. On theother hand, the amount of decomposable particles should not be so highthat the blowing operation is impeded or that the mechanical strength ofthe microsphere wall is weakened.

The macro particles may be added to the dispersed particle compositionin an amount of about 0.50 to 20%, preferably 1 to 10% and morepreferably 2 to 6% of the dispersed particles plus macro particlesvolume. The desired amount of macro pores can be obtained withoutsignificant weakening of the microsphere wall.

The use of the macro particles allows the creation in the microspherewall of macro pores of a predetermined size such that materials, such assolid or crystalline catalyst materials that are of a size of, forexample, 5 to 100 microns, can be given a ready access path into theinterior of the microsphere.

CERAMIC MATERIALS

The ceramic material used in the dispersed particle compositions fromwhich the hollow porous microspheres are made are generally those thatare presently known and used in the ceramic and catalyst industries.Ceramic materials, including metal oxides, that can be used as startingmaterials for making the microspheres are disclosed in Sowman U.S. Pat.No. 4,349,456. The selection of a particular ceramic material willdepend on the desired properties of the microsphere including catalystactivity of the microspheres, the ease of processing and theavailability and cost of the ceramic material or metal oxide material.For certain uses graphite particles can be used as the dispersedparticle ceramic material. The conventionally used ceramic materialssuch as Alumina (Al₂ O₃), Mullite (3Al₂ O₃.SiO₂), Cordierite (2MgO.2Al₂O₃.5SiO₂), Zircon (ZrO₂.SiO₂), and Zirconia (ZrO₂) can be used.Naturally occurring clay materials such as Kaolinite, montmorillonite,illite and bentonite can be used. The ball clay materials can also beused. A preferred ceramic material for use as dispersed particles isalumina (Al₂ O₃) sold by Alcoa under the trade names of Alcoa "A-16" and"A-17".

GLASS MATERIALS

The constituents of the glass material from which the dispersed particlecompositions can be made are widely varied to obtain the desiredphysical characteristics of the hollow glass microspheres. Theconstituents of the glass particles, depending on their intended use,can be synthetically produced glasses or naturally occurring glasses.The constituents of the glass can be selected and blended to havesufficient strength when hardened and solidified to support asubstantial amount of weight. Naturally occurring glass materials suchas basaltic mineral compositions can also be used. The use of thesenaturally occurring glass materials can in some cases substantiallyreduce the cost of the raw materials used. The glass materials disclosedin applicant's U.S. Pat. No. 4,303,431 can be used as starting materialsfor the hollow microspheres. The glass materials disclosed in the De VosU.S. Pat. No. 4,059,423 can also be used.

METAL MATERIALS

The hollow microspheres can also be formed from dispersed metalparticles such as iron, steel, nickel, silver, gold, copper, zinc, tin,tungsten, lead, aluminum, magnesium, cobalt, platinum and palladium andthe like, and mixtures thereof. The metals disclosed in the Schmitt U.S.Pat. No. 3,264,073 and in Farnard U.S. Pat. No. 3,674,461 can also beused as starting materials for the hollow microspheres.

METAL GLASS MATERIALS

There are a wide variety of metal glass alloy compositions which can beused as starting materials to make hollow porous metal glassmicrospheres. The term metal glass(es) as used herein is intended tomean the metal alloy materials and compositions which on rapid coolingfrom a temperature above their liquids temperature to a temperaturebelow their glass temperature can form amorphous solids. The metal glassalloys compositions have been broadly described as (1) metal-metalloidalloys, (2) transition metal alloys and (3) simple metal alloys. Theknown metal glass alloy compositions include precious metal alloys,alkaline earth metal alloys, rare earth metal alloys and actinide metalalloys. The dispersed metal glass particles can be made from the metalglass alloy materials disclosed in the applicant's U.S. Pat. No.4,415,512.

PLASTIC MATERIALS

The plastic materials that can be used as starting materials to makehollow porous microspheres are those disclosed in applicant's U.S. Pat.No. 4,303,603. Other plastic materials that can be used as startingmaterials are nylon, latex particles and aqueous dispersions of TEFLON(PTFE).

DESCRIPTION OF THE INVENTION

1. The microsphere catalyst can be prepared by coating or impregnatingthe hollow porous microspheres with the catalyst dissolved in an organicor inorganic solvent solution. The coating or impregnating step can becarried out by spraying the microspheres or immersing the microspheresin the coating or impregnating solution. The coating or impregnatingsolution displaces the air or gas within the hollow interior of themicrospheres, fills the hollow interior of the microsphere and the poresor interconnecting voids in the microsphere walls with the catalystsolution. The coated or impregnated microspheres are separted from thesolution, heated and dried to deposit the catalyst. This procedure canbe repeated, if desired, to build up the catalyst content in the centralcavity of the microsphere. The microspheres with the deposited catalystcan then be treated in a conventional manner to activate the catalyst bysubjecting them to a reducing atmosphere or an oxydizing atmoshpere atelevated temperature, or other treatment.

2. The microsphere catalyst can also be prepared by filling the catalystwith a support and then coating or impregnating the hollow porousmicrospheres and support with the catalyst. The hollow porousmicrospheres can be filled with a catalyst support by immersing themicrospheres in a solution, slurry or sol dispersion of the support and,e.g. applying pressure to the solution, slurry or sol dispersion. Themicrospheres can also be filled by placing the hollow porousmicrospheres on a porous belt, applying a suction under the belt andthen spraying or immersing the microspheres in the slurry or soldispersion. In each case the solution, slurry or sol dispersiondisplaces the air or gas within the hollow interior of the microsphere,fills the hollow interior of the microsphere and the pores orinterconncting voids in the microspheres walls with the solution, slurryor sol dispersion of the catalyst support. The microspheres can be, ifdesired, partially or entirely filled, or the pores or interconnectingvoids in the microsphere walls can be filled with the catalyst support.

The microspheres, after the filling step, are processed (i.e. dried,heated, washed, etc., as the case may be) as required to deposit thecatalyst support. The microsphere can then be heated to obtain thedesired physical characteristics of the catalyst support. The catalystsupport in finely particulate form is deposited on the inner wallsurface of the microsphere and/or fills the hollow interior of themicrospheres and the pores or interconnecting voids of the microspheres.The drying step removes the liquid phase of the slurry or sol from themicrosphere and the catalyst support forms small particles of catalystsupport which particles within the microsphere tend to agglomerate, asmall degree, during the drying step, thereby preventing them fromleaving the central cavity. The small particles in the pores orinterconnecting voids of the walls of the microsphere adhere to thesides of the interconnecting voids. The adherence of the catalystsupport to the sides of the interconnecting voids has the effect orreducing the pore size, i.e. the cross-sectional area of theinterconnecting voids and at the same time through the presence of thecatalyst support substantially increasing the surface area of theinterconncting voids in the microsphere walls. The filling of the hollowinterior of the mircosphere with catalyst support also substantiallyincreases the available surface area of the hollow porous microspheresfor deposit of catalyst.

The thus treated microspheres are futher treated by coating orimpregnating the hollow microspheres that now contain a catalyst supportwith catalyst. The catalyst can be applied by immersing the microspheresin a solution, slurry or sol dispersion of the catalyst in the mannerdiscussed above and filling the interior of the microsphere and theinterconnecting voids of the walls of the microspheres in a manner suchthat the catalyst support contained in the interior of the microsphereand in the interconnecting voids of the microsphere walls are completedcoated, or substantially completely coated with the catalyst. The hollowmicrospheres are separated from the catalyst solution, slurry or soldispersion and dried and if desired washed to remove any excess of thecatalyst. The hollow microspheres containing the catalyst on thecatalyst support can then be treated, as necessary, to activate thecatalyst, e.g. by calcining, and/or subjecting the catalyst to anoxydizing or reducing atmosphere.

3. The catalyst can be prepared by filling the microspheres withcatalyst or catalyst and catalyst support. The hollow porousmicrospheres can be filled with a catalyst or catalyst and catalystsupport by immersing the microspheres in a melt, slurry or soldispersion of the catalyst or catalyst and support, by placing themicrospheres on a porous belt, applying a suction under the belt andthen spraying or immersing the microspheres in catalyst or catalyst andcatalyst support melt, slurry or sol dispersion. The melt, slurry or soldispersion displaces the air or gas within the hollow interior of themicrosphere, fills the hollow interior of the microsphere and the poresor interconnecting voids in the microsphere walls with the melt, slurryor sol dispersion of the catalyst or catalyst and support. Themicrospheres can be, using the above described methods, partially orentirely filled, or only the pores or interconnecting voids in themicrosphere walls can be filled. The microspheres after the filling stepare heated and dried to deposit the catalyst or catalyst and support,and if desired washed. The dried microspheres can then be treated in aconventional manner, e.g. heated to calcine the catalyst or catalyst andsupport to obtain the desired physical and catalytic characteristics andproperties of the catalyst or catalyst and support.

The drying step removes the liquid phase of the slurry or sol dispersionand deposits the catalyst or catalyst and support within the hollowinterior of the microsphere and on the inner wall surface of themicrosphere and on the wall surfaces of the interconncting voids.

The catalyst or catalyst and catalyst support form small particles ofcatalyst or catalyst and support. The catalyst or catalyst and supportparticles within the microsphere tend to agglomerate, a small degree,during the drying and/or calcining step, thereby preventing them fromleaving the central cavity of the microspheres. The small particles ofcatalyst or catalyst and support in the pores or interconnecting voidsof the walls of the microspheres adhere to the walls of theinterconnecting voids. The adherence of the catalyst support andcatalyst to the walls of the interconnecting voids has the effect ofreducing the pore size, i.e. the cross-sectional area of theinterconnecting voids and at the same time through the presence of thecatalyst or catalyst and catalyst support substantially increasing thesurface area of the pores in the microsphere walls. The filling of thehollow interior of the microsphere with catalyst or catalyst and supportalso substantially increases the surface area of the catalyst availableto the reactant. The hollow microspheres containing the catalyst orcatalyst and support can then be treated as necessary to activate thecatalyst or catalyst and support, e.g. by subjecting the microsphere toa calcining step and/or a reducing or an oxydizing atmosphere.

4. The microsphere catalyst can be prepared by coating a support withthe desired catalyst and filling the hollow porous mircosphere with thecatalyst coated on the support. The catalyst on the support can bemilled or ground to an appropriate size and in the form of a slurry orsol dispersion used to fill the hollow microspheres. The microspherescan be filled with the catalyst on the support by immersing themicrospheres in a slurry or sol dispersion of the catalyst on thesupport, or by placing the microspheres on a porous belt, applying asuction under the belt and then spraying or immersing the microspheresin the slurry or sol dispersion of catalyst on support.

The slurry or sol dispersion catalyst fills the hollow interior of themicrosphere and the pores or interconnecting voids in the microspherewalls with catalyst. The microspheres can by using the above describedmethods, partially or entirely filled, and/or the pores orinterconnecting voids in the walls can be filled with catalyst.

The microspheres after the drying step are, if desired, washed. Thedried microspheres can then be further treated to activate the catalystor to otherwise obtain the desired physical and catalyticcharacteristics and properties of the catalyst on the support. Thedrying step, where a slurry or sol dispersion is used, removes theliquid phase from the slurry or sol and forms small particles of thecatalyst on support within the hollow interior of the microsphere. Thedrying step as mentioned above tends to a small degree to agglomeratethe catalyst particles, thereby preventing them from leaving the centralcavity of the microspheres.

The small particles of catalyst on support in the pores orinterconncting voids on the walls of the microspheres adhere to thesides of the interconncting voids. The heating steps enhance andstrengthen the adhesion.

The adherence of the catalyst on the support to the sides of theinterconnecting voids has the effect of reducing the pore size, i.e. thecross-sectional area of the interconnecting voids and at the same timethrough the presence of the catalyst on the support increasing thesurface area of the pores in the microsphere walls. The filling of thehollow interior of the microspheres with the catalyst on the supportalso substantially increases the surface area of the catalyst availableto the reactant. The microspheres containing the catalyst on the supportcan be treated as necessary to activate the catalyst, e.g. by subjectingthe catalyst to a calcining step or to an oxydizing or a reducingatmosphere.

5. The microspheres containing a catalyst can be coated with aninorganic selective membrane or for low temperature operations anorganic selective semipermeable membrane.

The microspheres containing a catalyst can be treated to coat at leastthe outer pore surface or area of the wall of the microsphere with aninorganic selective membrane. The inorganic selective membrane isapplied by coating the microspheres with a sol dispersion of the desiredcoating material. The particular sol dispersion material, particle sizeand concentration of the particles in the sol dispersion and thesubsequent heating temperature and time determine the micro pore size ofthe resulting inorganic selective membrane. The micro pore size can beselected to exclude specified materials, e.g. catalyst poisons and/or toselectively admit for contact with the catalyst, contained on and/or inthe hollow microspheres, specific chemical constituents of a reactantgas or liquid feed to the reaction. The use of an inorganic selectivemembrane allows use of the catalyst at relatively high temperatures.

The microspheres containing a catalyst can be treated to coat at leastthe outer pore surface or area of the wall of the microsphere with anorganic selective semipermeable membrane. The organic selectivemembranes have the advantage of a higher degree of selectivity beingobtainable but the restriction that they can only be used at relativelylow process reaction temperatures of, for example, about 300° to 400° C.The organic selective semipermeable membrane can be applied in themanner discussed in applicant's copending application Ser. No. 657,090filed Oct. 3, 1984 which is briefly discussed below.

The inorgaic selective membranes and the organic selective semipermeablemembranes prevent the catalyst encapsulated in the microsphere fromleaving the microsphere through the pores entrance means. Only specificliquids, gases and/or organic (or inorganic) molecules of predeterminedmolecular size which is smaller in size than the pore size of theselective membrane can enter or leave the single central cavity of themicrosphere through the selective membrane.

6. The microsphere catalyst can be used to carry out catalytic reactionsincluding petroleum hydrocarbon processes and chemical processes and tocarry out emission control processes.

In carrying out the present invention the catalyst or catalyst supportcan be applied to the hollow porous microspheres in the form of chemicalprecursors of the desired catalyst or catalyst support. The chemicalprecursors can undergo on the surface and/or in the central cavity ofthe hollow microspheres a chemical reaction, including a decompositionreaction to form the desired catalyst or catalyst support. The catalystor catalyst support can also be applied to the hollow microspheres inthe form of a melt of the catalyst or catalyst support. An example of amelt of a catalyst or catalyst support would be a high boilinghydrocarbon, which is subsequently heated and decomposed to form afinely divided active carbon. The finely divided active carbon canfunction either as a catalyst or catalyst support. Suitable precursorsfor the carbon particles are pitch and Saran. An example of a chemicalprecursor material which is decomposed to form a catalyst is an aqueoussolution of chloroplatonic acid which on drying the solution anddecomposing the chloroplatonic acid forms a deposit of platinum.

DESCRIPTION OF CATALYST

The hollow porous microspheres can be used as catalyst substrate andcatalyst containers for a wide variety of catalyst. For practicalpurposes, it is convenient to breakdown the use of catalyst reactionsinto three major categories: petroleum refining, chemical processes andemission control.

A brief description of the major categories of catalyst reactions andcatalysts used in each is provided below.

Petroleum Refining

Catalytic cracking--In the refining of petroleum hydrocarbons thecatalytic cracking of hydrocarbons is carried out primarily to increasethe yield of gasoline fractions. The principal catalyst used arealumina-silica and more recently natural and synthetically producedalumino-silicate zeolite molecular sieves. The catalytic crackingreaction can be carried out in a moving bed catalytic crackingapparatus.

Alkylation--In order to increase the yield of gasoline components C₃ andC₄ normal and isohydrocarbons are reacted in contact with concentratedsulfuric acid or hydrofluoric acid to produce C₇ and C₈ isohydrocarbons.

Hydrotreating--Hydrocarbon streams containing sulfur and/or nitrogen aretreated with a catalyst in the presence of hydrogen. The hydrotreatingis carried out to remove sulfur and/or nitrogen from a wide variety ofpetroleum fractions including naphtha, kerosene, gas oil and residualoil fractions. Hydrotreating catalyst include alumina impregnated withmolybdenum or tungsten oxide or molybdenum or tungsten sulfide as theactive component and cobalt oxide or sulfide or nickel oxide or sulfideas activity promoters.

Hydrocracking--Petroleum fractions are contacted with a hydrotreatingcatalyst in the presence of hydrogen to crack the feed to upgrade theproducts for use as gasoline, heating oil and kerosene, and to upgradefeed stocks for use in other processes. Hydrocracking catalyst includenoble metals such as platinum and/or palladium on an alumina ormolecular sieve zeolite support, and cobalt or nickel with tungsten ormolybdenum on an alumina or molecular sieve zeolite support.

Catalytic Reforming--Low octane components of petroleum fractions aretreated to form higher octane components, particularly for use asblending components in no-lead or low-lead gasolines. The reformingcatalyst used includes platinum or alumina support and platinum andrhenium on alumina support. Hydrogen gas is a principal by-product andis recovered for use in other refinery processes.

Chemical Processes

Polymerization--Polymerization processes are carried out to make highdensity polyethylene, polypropylene, linear low density polyethylene,polyvinyl chloride, polystyrene and urethane. The Ziegler-Natta catalystwhich are a combination of titanium or vanadium halide and alumina ormagnesium alkyl are used in the polymerization of polypropylene and highdensity polyethylene. Organic peroxides are used to initiate thepolymerization of various monomers to make low-density polyethylene,polyvinyl chloride and polystyrene. Polyurethanes are manufactured byusing organo-metals, e.g. organic tin compounds, and a tertiary aminecatalyst.

Oxidation Reactions--The production of nitric acid is carried out with anoble metal, e.g. platinum or palladium on a support. The production ofvinyl chloride is carried out with copper chloride on an alumina supportto carry out the oxychlorination step.

Hydrogenation--Olefin hydrocarbons, aromatic hydrocarbons and nitrohydrocarbons, edible and inedible oils, margarine, shortening and fattyamines are treated in the presence of a nickel catalyst and hydrogen toform the corresponding compounds with an increased hydrogen content.

Dehydrogenation--Styrene is produced from ethyl benzene in the presenceof a promoted iron catalyst. Hydrogen is a by-product of the reaction.

Emission Control

Automotive Exhaust--Automotive, truck and other internal combustionengine exhausts are treated to remove carbon monoxide, hydrocarbons andnitrous oxides (NO_(x)) from the exhaust. The catalyst uses noble metalssuch as platinum, palladium, rhenium and rhodium and mixtures thereof onceramic supports, such as alumina.

Industrial Waste Gases--Noble metals on supports as mentionedimmediately above are used to control emissions from incinerators,ovens, wood stoves and nitric acid plants.

Electric Power Generating Plant Stack Gases--activated carbon, carbonmolecular sieve and copper oxide catalysts are used to remove sulfurdioxide and nitrous oxides (NO_(x)) from stack gases.

The catalyst can be applied to the hollow porous microspheres in theform of solutions, sol dispersions and slurries of the catalyst. Thecatalyst can also be applied to the hollow porous microspheres in theform of chemical precursors of the desired catalyst. The chemicalprecursors after application to the hollow microspheres can be treatedto undergo a chemical reaction, including a decomposition reaction toform the desired catalyst.

The normally liquid catalyst, e.g. concentrated sulfuric acid used inalkylation reactions, can be treated to immobilize the catalyst, e.g.the catalyst can be treated with an inert colloid to gel the catalystand the gel catalyst can be applied to coat or fill the hollowmicrospheres. Alternatively, the microspheres can be coated or filledwith the liquid catalyst and then treated with an inert colloid to gelthe liquid catalyst. Examples of inert colloids that can be used aresilica, alumina and graphite.

The resin catalysts can also be used by coating or filling the hollowmicrospheres with the resin catalyst. Suitable resin catalysts are thoseproduced by the Rohm and Haas Company under the trade name Amberlyst.The Amberlyst catalyst resins are marketed in the form of smallinsoluble beads. Amberlyst 15, for example, is a sulfonic acid resinwhich can be used to catalyze esterification, hydration andoligerization reactions.

CATALYST SUPPORTS

In order to increase the activity of the catalyst, catalyst supportmaterials can be added to the hollow porous microspheres. The catalystsupports are those conventionally used in the art with the catalyst.Suitable catalyst supports include alumina, silica, silica-alumina,alumina silicate molecular sieve zeolites, finely divided carbon andcarbon molecular sieves. A readily available source of colloidal sizecatalyst support materials are the commercially available sol gelmaterials, colloidal powders, the ball clays and the bentonite clays.Further, there are now available in concentrations of 10 to 50 percentsolids, silica sols and metal oxide sols which are suitable for use ascatalyst supports.

The catalyst supports can be added to the microspheres in the form of asolution, sol dispersion or slurry of the support in a solvent, i.e.continuous phase. The catalyst supports can also be added to themicrospheres in the form of a melt. The solution, sol dispersion orslurry can be applied to the microspheres by coating or impregnating themicrosphere with the solution, sol dispersion or slurry. Themicrospheres can be treated with the support to completely fill themicrospheres, partially fill the microspheres, fill the pores andinterconnecting voids of the microspheres or to coat the outer wallsurface of the microspheres.

Where the entire microsphere is filled with, e.g. a high concentrationof a sol dispersion of alumina or silica particles in an aqueouscontinuous phase, the alumina or silica particles can be selected to beless than one half the size of the microsphere pores, or where macropores are present less than one half the size of the macro pores.

The microspheres can be completely filled with the sol dispersion andthen dried to remove the aqueous continuous phase. After drying themicrospheres containing the sol dispersion the microspheres can beheated to a temperature of 600° to 800° C. to remove the remainder ofany aqueous phase, and to sinter the dispersed particles to form withinthe single central cavity of the microspheres a lattice work of thesintered alumina or silica particles. The heating to 600° to 800° C. canalso activate the supports.

The lattice work continues from the central cavity, through theinterconnecting channels to the pores in the outer surfaces of themicrosphere's walls. In some applications, the lattice work of aluminaor silica particles are broken up by agitation of the microspheres toform in the central cavity loose agglomerates of the alumina or silicaparticles.

In another embodiment of the invention the microspheres may be filledwith only a sufficient amount of the sol dispersions such that thealumina or silica particles only deposit on the inner wall surface, inthe interconnecting voids and on the outer wall surfaces of themicrosphere's walls.

In still another embodiment of the invention the size of the catalystsupport particles in the sol dispersion or slurry are selected to be bigenough such that they do not pass through the interconnecting channels,but instead deposit on the outer wall surfaces and in the entrances onthe outer wall surfaces of the microsphere walls.

The catalyst supports can be applied to the hollow porous microspheresin the form of chemical precursors of the desired catalyst supports. Thechemical precursors after application to the hollow microspheres can betreated to undergo a chemical reaction, including a decompositionreaction to form the desired catalyst supports.

The catalyst support can be activated before or after adding thecatalyst to the hollow porous microsphere. The catalyst can be added tomicrospheres and catalyst supports in the form of a solution, soldispersion or slurry of the catalyst. The catalysts can also be added inthe form of a melt.

FILLING THE MICROSPHERE

The method used to fill the hollow porous microspheres with the catalystis dependent upon the particular system and must be conducted so thatthe activity of the catalyst is not adversely affected in the process.Prior to filling the microspheres with catalyst it may be necessary ordesirable to treat the microspheres to remove any residual amounts ofbinder material that may have been present during the microspheremanufacturing procedure.

In some cases it is sufficient to merely suspend the microspheres in aliquid carrier medium in which the catalyst is dissolved, suspended ordispersed, and to allow the catalyst to flow, or to diffuse by capillaryaction, through the entrance means or both the entrance means and poresin the walls of the porous hollow microspheres, depending on the size ofthe catalyst, into the hollow interior of the microspheres. Thesuspension can be gently stirred by mechanical mixing, to ensurehomogeneity of the system and uniformity of the amount of catalyst incontact with individual microspheres. It is also preferred that theliquid carrier be capable of wetting the material forming the walls ofthe microspheres to assist in the filling process. Wetting agents whichare inert to the catalysts can be added to the liquid carrier medium forthis purpose.

The concentration of the catalyst in the liquid carrier and the amountof catalyst relative to the total volume or number of the microsphereswill be selected depending on the nature and type of catalyst and thecatalytic process and on the internal volume of the microspheres and canbe readily determined by the skilled practitioner.

While the driving force of capillary action can be sufficient to fillthe hollow microspheres with the suspended, dispersed or dissolvedcatalyst, this technique often requires long times, on the order ofabout several hours, to fill all of the microspheres, and may not bepractical where the solid particles forming the microsphere walls anddefining the interconnecting voids or channels and the entrance meansare not sufficiently wetted by the liquid phase of the catalystsolution, suspension or dispersion.

Therefore, according to an embodiment of the invention, the drivingforce for filling the hollow microspheres with the catalyst and liquidmedium is increased by applying pressure to the system. The appliedpressure can be fluid pressure, e.g. hydrostatic pressure, isostaticpressure, pneumatic pressure or dynamic pressure, e.g. centrifugalforce.

Generally, the amount of the applied pressure will not be particularlycritical insofar as the pressure is not so great as to rupture the wallsof the microspheres and which will maintain flow of the catalyst-liquidmedium system into the microspheres. Pressures in the range of fromabout 3 psi to about 30 psi, preferably from about 5 psi to about 25 psihave been found to be satisfactory. Preferably, the pressure isincreased gradually. The pressure should be maintained until at leastsubstantially all of the microspheres are filled with the catalyst andliquid medium. Generally, the time required to fill the microsphereswill be inversely proportional to the applied pressure and to the sizeand number of entrance means and pores in the walls of the microsphereswhich connect the exterior of the microspheres to the hollow interior ofthe microspheres. Times on the order of from about 30 seconds to about60 minutes, generally from about 1 minute to about 40 minutes aresatisfactory.

One preferred filling method is to simply load a pressure vessel withthe microspheres and thereafter to fill the closed pressure vessel withthe catalyst-containing liquid medium under positive pressure using asuitable pressure pump.

Another method for filling the microspheres is to displace the gasnormally contained in the microspheres with a gas that readily dissolvesin the carrier liquid or catalyst solution, e.g. carbon dioxide orpropane.

In a preferred embodiment of the invention a relatively simple techniquefor filling the hollow microspheres is to "pull" the catalyst-liquidmedium system into the microspheres through the entrance means and/orpores. That may be done by forming a thin layer, preferably a single orseveral days, of the microspheres on a microporous sheet or belt andapplying a vacuum to the reverse side of the sheet or belt whereby thecatalyst-liquid medium system will be sucked into the hollow interiorspaces of the microspheres. If desired, a positive pressure cansimultaneously be applied to the catalyst-liquid medium system. The beltmay be a moving belt such that the filling procedure may be made to becontinuous.

In filling the central cavity of the microspheres using an appliedvacuum with, for example, colloidal size particles, it is found that thenon interruption of the flow of the particles, the direction of flow ofthe particles and the application of the vacuum are important. Thecontinuous flow in the same direction of the colloidal size particlesallows the particles to enter the microsphere from one side and allowsthe particles build up to occur inside of the central cavity on theopposite side of the microspheres until the central cavity is filledwith the colloidal size particles.

In filling the microspheres, it is generally sufficient to use an excessliquid medium and to carry out the filling operation for a period ofabout 20 to 60 minutes, preferably 30 to 40 minutes to assure adequatefilling of the microspheres with the dissolved or suspended catalyst andliquid medium.

Depending on the microsphere catalyst that it is desired to obtain, themicrosphere may be substantially completely filled with catalyst, onlythe interconnecting voids may be filled and the outer surface coated, oronly the outer surface may be coated with catalyst. Where themicrosphere is filled with catalyst, depending on the concentration ofcatalyst in the catalyst solution, slurry or sol dispersion, themicrospheres may contain solid particulate catalyst in the singlecentral cavity and/or the interior wall surfaces may have depositedthereon the catalyst.

Where a catalyst support is used, as discussed above, the catalyst isdeposited on the support. Generally the procedures for filling themicrospheres with catalyst are also applicable to filling themicrospheres with catalyst supports. The procedure used can be repeatedas desired to build up the catalyst or catalyst support contained in thecentral cavity of the microspheres.

CATALYST IMMOBILIZATION

After the microspheres are filled with catalyst it may be desirable ornecessary to treat the microspheres and catalyst to immobilize thecatalyst such that the catalyst is not readily removed from the hollowinterior of the microspheres.

The treatment required in each instance will depend on the particularcatalysts and whether the microspheres have microsphere pores ormicrosphere pores and macro pores.

In some situations it may be sufficient to merely agitate themicrospheres to cause sufficient agglomeration, e.g. loss of suspendingparticle charge leading to the development of cohesive forces, or anincrease in catalyst crystal or particle size, such that the catalyst isnot easily removed from the interior of the microspheres. In other casesagitation or agitation coupled with heating to a slightly elevatedtemperature is sufficient to obtain the desired agglomeration andincrease in catalyst particle size.

In another embodiment a small amount of an organic or inorganic bindermaterial is added to the catalyst sol dispersion or slurry, which ondrying the microspheres and catalyst provides sufficient adhesion of thecatalyst particles to each other that the catalyst particles areretained within the microspheres until the catalyst can be made toagglomerate or until the microspheres and catalyst can be treated toclose the microsphere entrance means with an immobilizing membrane. Theorganic binder is substantially removed during a subsequent heating stepto agglomerate the catalyst or to activate the catalyst. The inorganicbinder material can be removed or if inert to the catalyst reaction canbe allowed to be retained with the catalyst.

In an embodiment of the invention after the microspheres are filled withcatalyst, e.g. small solid particles, the hollow microspheres aretreated with a suitable solution, sol dispersion or slurry containing aninorganic dissolved or dispersed material suitable for forming aninorganic immobilizing membrane. The microspheres are then dried toremove the continuous phase and deposit on the outer wall surfaces andin the interconnecting voids of the microsphere walls small solidparticles. For example, where a silica sol dispersion is used to formthe immobilizing membrane, after treatment with the silica soldispersion, the microspheres are heated to a temperature of about 400°to 800° C. to fire and sinter the silica particles. The silica particleslink-up to form a porous lattice work of particles across theinterconnecting voids, sinter to the surface of the particles formingthe interconnecting voids and the firing removes the liquid phase fromthe dispersed silica particles.

The forming of a porous lattice work of sintered colloidal size silicaparticles in the interconnecting voids substantially decreases the sizeof the interconnecting voids and/or where macro pores are present in themicrosphere wall also substantially reduces the size of the macro poressuch that the catalyst contained in the hollow central cavity of themicrosphere is immobilized.

Various materials can be selected to form the immobilizing membrane,e.g. alumina, silica, metals, metal salts and ceramics. The materialselected is such that it will not adversely effect the catalyticactivity of the catalyst and such that it can withstand the conditionsof temperature and chemical environment to which the catalyst issubjected.

Accordingly, it is sufficient to use any inorganic immobilizing meanswhich will effectively retain the catalyst in the hollow interior of themicrospheres while permitting influx and outflow of liquids, gases,reactants, products and by-products, etc., which are required for theprocess and/or for the non-contamination of the catalyst.

INORGANIC SELECTIVE MEMBRANES

In another embodiment of the invention the material used to form theimmobilizing membrane can be chosen to deposit an inorganic selectivemembrane having a predetermined micro pore size. The pore size of theselective membrane can be chosen such that only selected constituents ofa process stream or chemical mixture are allowed to pass through themembrane and to come into contact with the catalyst and to react, whilethe remainder of the process stream or chemical mixture is preventedfrom contacting the catalyst. The use of a selective inorganic membranecan thus be used to combine in a single process a selection andseparation with a catalyst reaction. The use of the selective membranecan also lengthen the catalyst activity and catalyst life by excludingfrom contact with the catalyst materials that may tend to deactivate orpoison the catalyst.

Materials that are suitable for forming inorganic selective membranesare boehmite (gamma-AlOOH), alumina and silica.

ORGANIC SELECTIVE SEMIPERMEABLE MEMBRANES

In another embodiment of the invention where the catalyst reaction iscarried out at relatively low temperatures organic membranes may be usedas immobilizing and/or selective membranes. In accordance with thisembodiment, after the microspheres are filled with catalysts, e.g. smallsolid particles, the hollow microspheres are treated with a suitablesolution, sol dispersion or slurry containing an organic dissolved ordispersed material suitable for forming an organic immobilizingmembrane. The microspheres are then dried to remove the continuous phaseand deposit on the outer wall surfaces and in the interconnecting voidsof the microsphere walls a thin organic membrane. The organic membranecan be selected to be permeable to the reactants and reactant productswhile at the same time immobilizing the catalyst. The organic membranemay also be used to improve the catalyst selectivity by admitting onlycertain reactants.

The forming of the permeable organic membrane, seals off theinterconnecting voids and the macro pores in the microspheres wall suchthat the catalyst contained in the hollow central cavity of themicrosphere is immobilized.

Various organic materials can be selected to form the immobilizingmembrane, e.g. organic polymeric materials such as silicones, acrylics,and nylons. The materials are selected such that they will not adverselyeffect the catalytic activity of the catalyst and such that they canwithstand the conditions of temperature and chemical environment towhich the catalysts are subjected.

Accordingly, it is sufficient to use an organic immobilizing means whichwill effectively retain the catalyst in the hollow interior, will permitinflux and outflow of liquids, gases, reactants, products andby-products, etc. which are required for the process and will excludefrom the catalyst other materials, e.g. those materials that wouldcontaminate the catalyst.

In an embodiment of the invention the material used to form theimmobilizing organic membrane can be chosen to deposit an organicselective membrane having a predetermined permeability for molecularsize materials.

The permeability of the organic selective membrane can be chosen suchthat only selected constituents of a process stream or chemical mixtureare allowed to pass through the membrane and to come into contact withthe catalyst and to react, while the remainder of the process stream orchemical mixture is prevented from contacting the catalyst. The use ofan organic selective semipermeable membrane can thus be used to combinein a single process a selection and separation with a catalyst reaction.The use of the selective membrane can also lengthen the catalystactivity and catalyst life by excluding from contact with the catalystsmaterials that may tend to deactivate or poison the catalysts.

Any suitable method can be used for depositing the organic semipermeablemembranes. For instance, the microspheres can be immersed in a dilutesolution of a film-forming polymer or a polymer forming system,preferably while applying mild agitation to the mixture to ensurehomogeneity and uniform formation of the film on all of themicrospheres. It is also preferred to carry out the contact with a smalloverpressure on the system to force the polymer film into themicrospheres pores and macro pores, as well as between and among theindividual sintered particles of the microsphere walls defining themicrosphere's interconnecting channels, this serving to strengthen thebond between the formed membranes and the microspheres. It should benoted that the application of pressure to the film forming solution inwhich the microspheres are immersed can be analogized to the applicationof a vacuum to the bore of hollow porous filaments to which apermselective polymer coating is applied from the exterior, such astaught in U.S. Pat. Nos. 4,230,463, and 4,214,020. The coating processis generally suitable for applying a depositable film forming materialto form a deposit of a semipermeable membrane in the microsphere poresand macro pores of individual microspheres over essentially the entiresurface areas of the hollow microspheres. The deposited films aresufficiently thin to provide high flux rates of reactant gas or liquidconstituents having a molecular size below the "cut-off" size or"cut-off" molecular weight of the deposited semipermeable film. The"cut-off" size or weight refers to the maximum molecular size or weightof reactant constituents which can diffuse through the semipermeablemembrane.

In further detail, the depositable material, i.e., a material suitablefor forming the coating, desirably has a sufficiently large molecularsize (if dissolved in the solvent) or a sufficiently large particle size(if suspended in the solvent, e.g. as a colloidal dispersion) that thedepositable material does not readily pass through the pores in thewalls of the hollow microspheres when subjected to pressure. Thus, withmicrospheres having pores of generally larger diameters, depositablematerials which have larger sizes when in the coating liquid arefrequently desired. In some instance, it is desirable to employdepositable materials which, when in the liquid vehicle, havesufficiently small sizes that they can enter, instead of bridge, poresin the microspheres. The depositable material may directly form thecoating when deposited, or the deposit of the depositable material maybe further treated, e.g. by cross-linking, to form the desired coating.

The coating liquid generally comprises a solvent (or vehicle) for thedepositable material. The solvent should be capable of dissolving thedepositable material or be capable of suspending a finely-divideddepositable material, e.g. having particle diameters less than about 1micron, e.g. about 5000 angstroms (i.e., colloidal size). Desirably, thecoating liquid contains substantial amounts of solvent, e.g. a majoramount of solvent, such that during deposition of the depositablematerial on the hollow microspheres, depositable material, which is notforcibly retained in the microsphere pores and macropores due toadhesion to the solid wall material and/or due to the presence of theapplied pressure, can be redissolved or otherwise removed from thehollow microspheres. Also, the coating liquid contains sufficientamounts of solvent such that the coating liquid exhibits a viscosity attemperatures employed in the coating which viscosity is advantageouslylow to enable relatively rapid, adequate permeation of the coatingliquid through a dense mass of the microspheres.

The contact of the coating liquid containing the depositable materialwith the mass of microspheres in order to effect the desired depositionis advantageously provided by immersion of the microspheres in thecoating liquid. The immersion of the hollow microspheres in the coatingliquid may be effected in any suitable manner. For instance, the mass ofmicrospheres may be poured into the coating liquid. However, it isgenerally preferred that the coating liquid be added to a retainingvessel containing the mass of microspheres.

The coating liquid may be unagitated or may preferably be agitated, e.g.by circulating the coating liquid through the retaining vessel to assistin maintaining the suspension of the depositable material (if thedepositable material is in particulate form in the coating liquid) andin providing desirable distribution of the coating liquid through themicrosphere mass.

The hollow microspheres can be subjected to the applied pressure fromthe exterior to the interior at least while immersed in the coatingliquid. The pressure drop is desirably maintained for a time (eitherintermittent or preferably continuous) sufficient to provide the desireddeposit.

After the removal of the coated microspheres from the coating liquid,the microspheres may be immersed in at least one additional coatingliquid, which additional coating liquid may or may not be essentiallythe same as that of the first coating liquid, in order to provide two ormore coatings on the hollow microspheres or to chemically affect atleast one preceding deposit, e.g. by cross-linking or the like.Cross-linking or other procedures which chemically affect the depositmay be provided by contact with a suitable liquid or gaseous agent. Thedeposits on the hollow microspheres may or may not be dried (i.e. theremaining solvent removed) or otherwise treated intermediate theimmersions.

The resulting coating (or coatings) are relatively uniform throughoutall the pores and interconnecting voids and macropores. Generally, thecoating has an average thickness of up to about the microsphere wallthickness, preferably about 1/2 to 1/50 of the microsphere wallthickness. Frequently, the average thickness of the coating is less thanabout 5, and may even be about 1 micron or less. Advantageously, thecoating is substantially permanent in the pores and interconnectingvoids and macropores and thus does not unduly separate from the hollowmicrosphere during storage or use of the microspheres in carrying outcatalytic reactions.

The hollow microspheres prior to being coating are porous, i.e. havecontinuous channels for fluid flow extending between the exterior andinterior surfaces. Frequently, the microsphere pores have an averagecross-sectional diameter of from about 1000 to about 50,000 angstroms(0.1 to 5 microns) and in some hollow microspheres, the cross-sectionaldiameter of the pores or interconnecting voids can be about one to about5 microns.

Passage across the semipermeable membrane can be by chemical ormolecular diffusion and/or by solvation and evaporation and is dependenton the molecular spacing of the coating material and the materialpermeating through the membrane.

CONTINUOUS LIQUID PHASE

The liquid phase for the solutions, slurries or sol dispersionsdescribed herein can be aqueous or non-aqueous. The liquid phase can setas a solvent for one or more of the ingredients, for example, thecatalysts, the catalyst supports, the binders for the catalyst supportsor catalysts, the immobilizing membrane precursors or the selectivemembrane precursors.

The aqueous liquid phase can comprise water and/or water and watersoluble solvents. The binders that can be used for catalyst or catalystsupports in aqueous continuous liquid phase compositions include acrylicpolymers, acrylic polymer emulsions, ethylene oxide polymer, hydroxethylcellulose, methyl cellulose, polyvinyl alcohol and xanthan gum.

The non-aqueous liquid phase can comprise organic solvents such asacetone, ethyl alcohol, benzene, bromochloromethane, butanol, diacetone,ethanol, isopropanol, methyl isobutyl ketone, toluene, trichloroethyleneand xylene.

The binder materials that can be used for catalyst or catalyst supportsin non-aqueous liquid phase compositions include cellulose acetate,butyrate resin, nitro cellulose, petroleum resins, polyethylene,polyacrylate esters, polymethyl methacrylate, polyvinyl alcohol,polyvinyl butyral resins, and polyvinyl chloride.

The binder materials are used in a relatively small amounts to retainthe catalyst support and/or catalyst in the hollow porous microspheresduring the agglomeration steps and/or calcining step and will generallybe removed during the calcining step.

DISPERSING AGENTS

Where slurry or sol dispersion particles, e.g. catalyst or catalystsupports are in the colloidal size range of 0.005 to 0.1 microns in sizeand they have an affinity for the continuous liquid phase or if theyhave like surface charges, they can naturally form a stable dispersionand an added dispersing agent may not be needed. Also, when the slurryor sol dispersion particles are formed in situ just before or just afterthe particles are deposited on or in the hollow microsphere an addeddispersing agent may not be needed. However, for ease of handling andfor maintaining the dispersed particles, particularly particles above0.1 to 1.0 microns in size, in a stable slurry or sol dispersion adispersing agent is usually added.

When the dispersed particles are smaller than about 0.005 microns theparticles begin to assume the properties of a true solution. When theparticles are greater than 0.1 micron there is a natural tendency forthe particles to separate out of the liquid phase and a dispersing agentand/or continuous stirring of the dispersed particle composition is orare required up until just before applying the slurry or sol dispersionto the microspheres.

A sufficient amount of dispersing agent is added such that the dispersedparticles form a stable dispersion for a period long enough to apply theslurry or sol dispersion to the hollow microspheres.

Dispersing agents that are suitable for use with aqueous continuousliquid phase compositions are the commercially available sodium alkyland sodium aryl sulfonic acids. Another dispersing agent that can beused is sold under the trade name Darvan-7 which is a sodiumpolyelectrolyte, and is available from R. T. Vanderbilt Co., 230 ParkAvenue, New York, NY 10017. Organic carboxylic acids and organicpolycarboxylic acids, e.g., citric acid, can be added to maintain adesired pH, and function as dispersing agents.

Dispersing agents that are suitable for use with non-aqueous, e.g.,organic solvent, continuous liquid phase compositions are generallythose used in the industry, e.g., fatty acids (glyceryl tri-oleate),Menhaden Fish Oil (Type z-3, sold by Jesse Young, Co.) and thecommercially available benzene sulfonic acid surfactants.

EXAMPLES

The following examples illustrate the preparation of microspherecatalysts and applications of microsphere catalysts for carrying outcatalytic reactions in accordance with the present invention.

EXAMPLE 1

An auto emission control catalyst is prepared in accordance with thepresent invention by impregnating hollow porous microspheres containingmacro pores with precious metal catalysts or mixtures thereof.

The hollow porous microspheres are prepared from an alumina dispersedparticle composition following the procedure of applicant's copendingapplication Ser. No. 639,126. The alumina particle composition aluminaparticles 0.1 to 5.0 micron in size. The dispersed particle alsocontains combustible macro particles about 100 microns in diameter. Thehollow porous microspheres used are 1500 to 2000 microns in diameter andabout 40-80 microns wall thickness and contain a multiplicity of macropores about 100 microns in diameter.

The use of hollow, as distinguished from solid microspheres as thesubstrate for the catalyst substantially increases the heat-up rate ofthe catalyst bed upon engine start-up and reduces the rate at which theabutting bodies abrade catalyst from the surfaces of each other due tovibration and road shock. All of this because of the substantialreduction in the weight of the microspheres by reason of their beinghollow.

The particular choice of catalytic agents used depends upon theperformance characteristics desired in the system. Principally the noblemetals platinum, palladium and rhodium and mixtures thereof are used inautomobile exhaust emission control.

The catalyst can contain platinum alone, palladium alone, mixtures ofplatinum and palladium, mixtues of platinum or palladium with rhodium ormixtures of platinum and palladium and rhodium. Where the mixed catalystcomprises platinum and palladium they can be used in amounts of platinum65-75% and palladium 25-35% by weight. Where rhodium is added toplatinum or palladium, or to platinum and palladium it is added in anamount of 5-15% by weight of catalyst.

Where a mixture of platinum and palladium is used the hollow porousmicrospheres can be impregnated with a platinum and palladium solutiongenerally following the procedue described in Sanchez U.S. Pat. No.4,390,456. To prepare a suitable auto emission catalyst 2000 grams ofmicrospheres are impregnated with a solution which is prepared asfollows: SO₂ is bubbled into 800 ml. of deionized water for 20 minutesat 1 m. mole/minute after which about 4.2 ml. of Pd/(NO₃)₂ solutioncontaining 100 mg. palladium per ml. is added. The resulting solution isyellowish green indicating complexing of the palladium. A solution ofammonium platinum sulfito salt, (NH₄)₆ Pt(SO₃)₄.H₂ O, is prepared bydissolving about 4.0 g of the platinum salt having a platinum content ofabout 31.0% in 800 cc water. The palladium solution is then added to theplatinum solution. The total volume is then increased to about about2000 ml. by the addition of additional deionized water. The solution isthen used to impregnate the microspheres by contacting the microspheresuntil the microspheres are saturated with catalyst solution.

The microspheres are separated from the catalyst solution and allowed todrain dry after which they are placed in an oven and dried at 300°-350°F. for one to two hours. After drying the catalyst is activated byheating at 800°-900° F. for one to two hours in air.

The hollow porous microspheres have platinum and palladium deposited onthe inner and outer microsphere wall surfaces. The catalyst is alsodeposited in the interconnecting channel surfaces in the microspherewalls. The microsphere pores of a size of about 1.0 to 5.0 micron andthe macro pores of about 100 microns size provide ready access of thecombustion gases to the catalyst sites in the interconnecting voids andon the inner wall surface of the microspheres.

The microsphere catalyst can be placed in a suitable container orcatalytic converter and installed in an engine exhaust line system. Thecatalytic converter can be designed to have a straight-through flow, across-flow, or a radial flow and may be used alone or in combinationwith a conventional type of acoustic muffler. Combustion air can beinjected ahead of the converter inlet by use of an aspirator means or byan external compressive means.

At an operating temperature of the catalyst of 200° to 300° C., the COand hydrocarbon content in an automobile exhaust are each reduced by atleast 30 to 50% by volume. The CO is converted to CO₂ and thehydrocarbons converted to CO₂ and H₂ O.

In another embodiment of the invention the hollow microspheres are firsttreated with a sol dispersion of alumina particles to the point ofsaturation. The microspheres are then heated to dry the microspheres anddeposit the alumina particles as an alumina support. The aluminaparticles deposite on the inner and outer microsphere wall surfaces andon the surfaces of the dispersed particles that form the interconnectingchannels in the microsphere walls. The microspheres are then furtherheated to activate the alumina support. The microspheres containing theactivated alumina support are treated as described immediately above todeposit palladium and platinum catalyst on the alumina support. Themicrosphere catalyst are tested as before and are found to substantiallyreduce the hydrocarbon and CO content of an automobile exhaust stream.

In another embodiment the hollow microspheres are coated with platinumand palladium chloride solutions generally following the proceduredescribed in Watson et al U.S. Pat. No. 4,039,480. The microspheres areimpregnated with the solution after which the impregnating solution isevaporated. As the solution is evaporated, metallic salts are depositedon the inner and outer wall surfaces of the microspheres and on thesurfaces of the interconnecting channels in the walls forming saltcrystals. After drying the microspheres are heated at 900°-1000° C. for1 to 2 hours in an oxidizing atmosphere to decompose the metal salts toelemental Pt and Pd. The thus prepared catalyst can be used in acatalytic converter as before.

In another embodiment of the invention where reduction of nitrous oxidesin the exhaust is a primary concern, the catalyst solutions taught inthe Stenzel et al U.S. Pat. No. 4,077,908 can be used to impregnate themicrospheres. For example, a mixtue of Cu(NO₃)₂.3H₂ O, Ni(NO₂)₂.6H₂ Oand Mn(NO₃)₂.4H₂ O in solution can be used to impregnate the hollowporous microspheres. The impregnated microspheres are dried and thentreated to activate the catalyst. The microsphere catalyst can be usedas before for auto emission control.

The emission control catalyst in addition to being used in variousvehicle exhaust systems, can be used in stationery engine systems, suchas generators, auxilary power in power boats, in chemical or industrialprocesses in which carbon monoxide, hydrocarbons and nitrous oxides arethe principal combustion product pollutants.

EXAMPLE 2

Hydrodesulfurization and/or hydrodenitrogen catalysts are prepared inaccordance with the present invention by first impregnating hollowporous microspheres with an alumina support and then impregnating thehollow porous microsphere containing the alumina support with a solutioncontaining cobalt-molybdate or a solution containing nickel-molybdate.The hollow porous microspheres are used as a substrate for acobalt-molybdenum or nickel molybdenum catalyst deposited on an aluminasupport.

Hollow porous microspheres are made from an alumina dispersed particlecomposition. The microspheres are 2000 to 4000 microns in diameter and40 to 80 microns wall thickness. The microspheres are made in accordancewith the method described in applicant's copending application Ser. No.639,126. The hollow porous microspheres are substantially uniform indiameter and substantially uniform in wall thickness and porosity. Themicrospheres are examined and it is found that the microsphere wallshave a 25-30% porosity and uniform distribution of interconnectingvoids, and that the microspheres are rigid and have relatively highstrength, requiring in excess of 500 psi at point to point contact tobreak the microspheres. The microsphere pores, i.e. the openings in theouter wall surface, a cross-section of the interconnecting pores and theopenings on the inner wall surface are examined and are about 1 to 3microns. If desired, the microspheres can be made to also contain macropores 80 to 100 microns in diameter.

To prepare an alumina catalyst support an aqueous alumina sol dispersioncontaining an about 25 weight percent alumina particles, e.g. 12 to 17volume percent of the sol dispersion, in the range of 0.05 to 0.1microns in size is contacted with the hollow porous microspheres on aporous bed. A suction is applied under the bed to draw the alumina soldispersion into the single central cavity of the microspheres and tofill the microspheres. The microspheres are dried at about 65°-100° F.and then washed to remove excess alumina sol dispersion.

The washed and dried microspheres are then gradually heated to atemperature of 260° C. to 900° C. to calcine the alumina support. Thealumina particles on heating sinter together at their points of contactto form a porous latticework of alumina particles in the single centralcavity, in the interconnecting voids and bridging the microsphere poreson the outer wall surface of the microspheres and the microspheres poreson the inner wall surface of the microsphere walls. The porous latticework of alumina particles made from the alumina sol dispersion comprisesabout 80% void content and has a pore size of up to 200 microns. Thepore size measured is that between clusters of adjacent aluminaparticles in the latticework formed by the alumina sol dispersion. Thealumina support is immobilized in the latticework and is now ready forimpregnation with an active catalyst. In another embodiment, themicrospheres may be subjected to vibration during drying to partiallybreak-up the alumina support latticework. The latticework is broken upinto alumina particle clusters 50 to 200 microns in size with acorresponding reduction pore diffusion resistance.

The hollow porous microspheres to be useful for hydrodesulfurization orhydrodenitrogenation should contain at least one hydrogenation agent andpreferably contain a combination of two such agents. The metals and/orthe metal sulfides and oxides of molybdenum and tungsten, and the metalsand/or the metal oxides and sulfides of cobalt and nickel, aresatisfactory hydrogenation agents. Combinations of nickel-molybdenum andnickel-tungsten are preferred for hydrodenitrification and thecombination of cobalt-molybdenum is preferred for hydrodesulfurization.

The catalyst can be incorporated into the calcined support by any of thewell-known methods, preferably by impregnation ordinarily employed inthe catalyst preparation art.

A suitable catalyst is made by impregnation of the alumina support usinga solution of a cobalt or nickel salt and phosphomolybdic acid. Thecobalt or nickel content should be in the range of 2-5 parts calculatedas the pure metal and the molybdenum or tungsten content should be 5-20parts calculated as a pure metal based on weight of catalyst and aluminasupport. It should be understood that the metal catalyst can be presentin the final catalyst in the compound form such as the oxide or sulfideform as well as the elmental metal.

The hydrodesulfurization or hydrodenitrogenation catalysts of thisinvention are suitable for hydrotreating heavy hydrocarbonaceous feedssuch as coal liquids or fractions resulting from the dissolution ofcoals, e.g. bituminous coals. Other suitable feeds for desulfurizationinclude hydrocarbonoceous products or fractions from tar sands, shaleoil and petroleum, including atmospheric or vacuum residual, toppedcrude, reduced crude, solvent deasphalted residual, as well asdistillate material such as vacuum gas oil from petroleum, etc.

The processing of hydrocarbonaceous feed stocks according to thisinvention requires that the feed stock be contacted with a fixed ormoving bed containing the microsphere catalyst of this invention underhydroprocessing conditions, as are well known in the art, for examplethose disclosed in Kyan U.S. Pat. No. 4,342,643 and MacLaren U.S. Pat.No. 2,912,375. Suitable hydroprocessing conditions include temperaturesof 250° C.-450° C., pressures of from 30-200 atmospheres and hydrogengas rates of 2000 to 12000 standard cubic feet of hydrogen per barrel offeed stock.

A microsphere catalyst containing cobalt and molybdenum on an aluminasupport is tested for hydrodesulfurization activity by contacting thecatalyst with a California vacuum distillate gas oil containing 1.2%organic sulfur. The hydrodesulfurization conditions are temperature ofabout 350° C., about 30 atm. total pressure and about 6000 standardcubic feet of hydrogen per barrel of oil feed. The desulfurized productis tested and the sulfur contact is found to be substantially reduced,e.g. to a level below about 0.50 weight percent sulfur.

The hydrodesulfurization and hydrodenitrigenation processes canadvantageously be carried out using the process and apparatus describedin MacLaren U.S. Pat. No. 2,912,375. The MacLaren patent describescarrying out continuous desulfurization or denitrification process in amoving bed followed by a continuous catalyst regeneration step.

EXAMPLE 3

A hydrocracking catalyst is prepared in accordance with the presentinvention by impregnating hollow porous microspheres with a compositioncomprising a sol dispersion of silica particles in a solution of nickeland aluminum. The silica particles form a support for a nickel-aluminacatalyst. The hollow porous microspheres are used as a container for anickel-alumina catalyst deposited on a silica support. The hollow porousmicrospheres having 2000 to 4000 micron diameter and a 40 to 80 micronswall thickness are used. The microspheres can contain macro pores 40 to80 microns in diameter.

The nickel-alumina on silica support catalyst can be prepared bygenerally following the method described in Kyan U.S. Pat. No. 4,342,643and 3,673,079. For example, aluminum oxide is reacted with hydrochloricacid and water to form a 20% aluminum chloride solution. Nickel powderis reacted with HCI and water to form an about 30% nickel chloridesolution. About five hundred eighty-six grams of aluminum chloridesolution are put into a container. To this is added about 250 grams ofthe nickel-chloride solution and about 180 grams of glacial acetic acid.A second solution is made by diluting about 1150 grams of sodiumsilicate with about 2 liters of water. A dilute solution of the sodiumsilicate is added slowly to the first solution with stirring to form asilica sol in an aluminum and nickel chloride solution. The silicasol-nickel-aluminum solution is then used to fill the single centralcavity of the hollow porous microspheres.

The filled microspheres are removed from the silica sol-nickel-aluminumsolution and are contacted with a dilute aqueous ammonia solution (16.5wt.% NH₄ OH). The ammonia solution reacts with the nickel and aluminumto form a gel of the corresponding nickel and aluminum hydroxides. Theammonia contact is continued until a pH 7.5 is reached. The microspheresare washed to remove excess ammonia. The microspheres are then heated toa temperature of about 120° C. to remove excess water and further heatedto a temperature of about 300° to 800° C. to calcine the silica-aluminaand nickel catalyst.

The finished catalyst contains about 6 weight percent nickel and about12 weight percent alumina on the silica support. The catalyst issuitable for hydrocracking hydrocarbonaceous feeds to produce lowerboiling materials. Suitable feed stocks for hydrocracking includedistillates such as vacuum gas oil and metal containing distillates frompetroleum, coal-derived liquids, and hydrocarbonaceous materials fromtar sands and shale oils. Hydrocracking is also performed on residualpetroleum feed stocks such as atmospheric and vacuum residual fractions.

Alternatively, the ammonia treating step can be omitted and themicrospheres dried and heated to precipitate the catalyst. The nickeland aluminum precipitate on a silica latticework as nickel oxide andalumina (Al₂ O₃). The silica during the drying and calcining step formsa highly porous latticework of silica particles in the single centralcavity of the microsphere with the nickel oxide and alumina depositedthereon.

The microsphere catalyst can be used to carry out hydrocrackingprocesses under conventionally used hydrocracking process conditions,for example, the conditions disclosed in Price, et. al., U.S. Pat. No.3,159,568 of temperatures of about 650° to 850° F. (343° to 454° C.),pressures of about 500 to 2000 psig, hourly space velocities of about0.5 to 8.0 volumes of liquid feed per volume of catalyst and hydrogenratios of about 500 to 15000 standard cubic feet of hydrogen per barrelof hydrocarbon feed.

EXAMPLE 4

A molecular sieve catalytic cracking catalyst is prepared in accordancewith the present invention using hollow porous microspheres ascontainers for 13Y crystalline zeolite molecular sieve catalyst. Thehollow porous microspheres are made following the procedure described inapplicant's copending application Ser. No. 639,126.

Hollow porous microspheres are made from an alumina dispersed particlecomposition. The microspheres are 2000 to 4000 microns in diameter and40 to 60 microns wall thickness. The dispersed particle composition usedto make the hollow porous microspheres contains about 2-4 volume percentof vaporizable macro particles about 60 to 80 microns in size. Thehollow porous microspheres contain a multiplicity of macro pores about60 to 80 microns in diameter. The microsphere pores are about 1-3microns and the microspheres have a wall porosity or void content ofabout 30-35%.

A 40-60 weight percent slurry of Na-13Y zeolite molecular sieve isprepared from a finely divided Na-13Y zeolite crystalline powder. TheNa-13Y zeolite crystals are 1-10 microns in size and have a pore size ofabout 0.7 to 0.9 mm (0.0007 to 0.0009 microns). The hollow porousmicrospheres, in a layer one to three microspheres deep, are placed on aporous moving belt and a suction is applied to the bottom side of theporous belt. The slurry of Na-13Y zeolite is sprayed onto themicrospheres to saturation. The suction applied beneath the porous beltcauses the slurry to fill the single central cavity of the microspheres.The slurry passes into the central cavity primarily through the macropores entrance means in the microsphere wall. After the microspheres arefilled with the slurry, the microspheres containing the Na-13Y zeoliteslurry are treated to remove the carrier vehicle. This step causessufficient agglomeration of the Na-13Y sieve crystals such that thecrystals are not easily removed from the single central cavity of thehollow microspheres. The carrier vehicle used to form the slurry can beorganic or inorganic and will have a low solubility for the zeolite.

The hollow porous microspheres containing the Na-13Y sieve crystals arethen treated to cation to exchange the Na for the lanthanum series rareearth elements, e.g. lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium and gadolinium. The cation exchange ofthe Na for lanthanum series rare earth elements to make crackingcatalyst is well known and conventional in the art. The rare earthcation exchange is carried out for a sufficiently long period that allor substantially all the sodium cation is removed. After the rare earthcation exchange reaction is completed the microsphere containing therare earth 13Y-zeolite is heated to dry the molecular sieve and tofurther agglomerate the zeolite crystals to a size such that thecrystals do not come out of the macro pores. The microsphere catalystcan be further treated as in conventional in the art to activate orotherwise prepare the catalyst for use in a catalytic cracking process.

The microsphere catalyst containing the rare earth-Y zeolite catalyst iseffectively a binderless pellet. The hollow porous microsphere providesa strong protective porous outer shell which protects the crystallinezeolite from attrition while the crystalline zeolite without theconventionally used diffusion limiting binder material can moreeffectively and efficiently carry out the desired catalyst reaction.

In zeolites the catalysis takes place within the intracrystalline voidstructure of the zeolites. The catalytic reaction takes place at theactive catalyst sites by diffusion of reactants to the sites andproducts from the sites.

In the prior art catalyst, the binder used to form pellets affect thecatalytic reactions because of the need of reactants and products todiffuse into and out of the binder used to form the pellets. The abilityto form a catalyst without the use of a binder substantially increasesthe diffusion of reactants and products into and out of the crystallinezeolite structure.

The microsphere catalyst containing rare earth Y-zeolite offer theadvantages of high strength, high attrition resistance, high rates ofinter molecular hydrogen transfer coupled with extremely high intrinsiccracking activity and the high thermal stability of the zeolite crackingcatalyst.

The rare earth Y-zeolite microsphere catalyst can be used to crackhydrocarbon petroleum fractions in conventional cracking processes, e.g.fixed or moving bed processes in a mixture with conventionalsilica-alumina cracking catalyst, to increase the yield of light cycleoil, the yield and octane of the gasoline product fraction, and decreasethe production of coke. The high cracking rates that are obtained withthe zeolite catalyst results in greatly reduced contact times for givenconversion levels, thus further increasing liquid-product yields. Anadditional advantage obtained with the zeolite catalyst contained in thehollow microsphere is greater operating flexibility.

The catalytic cracking process conditions that can be used areconventional in the art, for example, temperatures of about 300° to 600°C. and pressures of about 30 psia to 200 psia.

The NA-13Y and Na-13X crystalline molecular sieve zeolites can also becation exchanged with magnesium, calcium or zinc, or with NH₄ ⁺ andconversion to the acid form. These catalyst can be used as hydrocrackingcatalyst. The hydrocracking process conditions that can be used areconventional, for example, those disclosed in Price, et. al., U.S. Pat.No. 3,159,568 of temperatures of about 450° to 700° F. (232° to 371° C.)and pressures of about 500 to 1500 psig.

EXAMPLE 5

The hollow porous microspheres of the present invention are used in atwo step process to treat stack gas from a coal fired or oil firedelectric power generating station to selectively remove and recover SO₂from the stack gas and to convert nitrogen oxides (NO_(x)) in the stackgas to nitrogen (N₂).

In the first step of the process the stack gas is contacted with hollowporous microspheres containing finely divided molecular sieve carbonparticle catalyst having a large surface area to catalytically convertthe SO₂ to H₂ SO₄ and to catalytically reduce the nitrogen oxides tonitrogen. The H₂ SO₄ is adsorbed by the carbon catalyst. The carboncatalyst containing the adsorbed H₂ S₄ is treated and a gas streamcontaining concentrated SO₂ and CO₂ is desorbed.

In the second step of the process the concentrated SO₂ and CO₂ gasstream is contacted with hollow porous microspheres containing anabsorbent which is a selective solvent for SO₂, e.g. polyethylene glycol(PEG). The polyethylene glycol has a high selectivity and highsolubility for SO₂ over CO₂. The SO₂ and CO₂ gas stream is contacted atelevated pressure with the microspheres containing the polyethyleneglycol absorbent particles and the SO₂ is selectively dissolved in thepolyethylne glycol. On reducing the pressure to about atmospherepressure the SO₂ comes out of solution in the polyethylene glycol, isseparated, repressurized and is recovered as liquid SO₂ product.

The hollow microspheres of the present invention allow the use ofmaterials as catalyst, adsorbents, absorbents or solvents whichheretofore could not be used as effectively as catalyst, adsorbents,absorbents or solvents. This is accomplished by encapsulating thecatalyst, adsorbents, absorbents or solvents within the single centralcavity of the hollow porous microspheres. Where the catalyst, adsorbent,absorbent or solvent is a liquid, a thickener is added to the liquid toform an immobilized liquid membrane or coating on and/or in the hollowmicrosphere.

Heretofore the use of finely divided carbon particles as catalysts orsorbents had been restricted because the particles were weakstructurally, had high attrition rates and we elutriated from theprocess. There was also the risk of combustion of the finely dividedcarbon particles during regeneration of the carbon catalysts or sorbent.

In prior uses of finely divided molecular sieve carbon particles, forexample, in the "char" process, degradation of the carbon particlesoccurred because of weakening and attrition of the particles due toexpansion of the particles during repeated adsorption and desorptioncycles. The combustability of the carbon particles during the hightemperature regeneration, i.e. desorption cycle also causes degenerationof the carbon particles. It was also found that there was an increase insize of the carbon pores and a corresponding decrease in physicalstrength of the carbon particles due to continuous adsorption anddesorption cycles which lead to weakening and the ultimatedisintegration of the carbon particles.

The encapsulation of the finely divided molecular sieve carbon particlescatalyst within the single central cavity of the hollow porousmicrospheres in accordance with the present invention protects thecarbon particles from attrition, reduces the contact of the carbonparticles with combustion gas, i.e. oxygen in the process stream, andgenerally protects the carbon particles during the process adsorptionand desorption cycles. The entrance means, i.e. the microsphere poresand macro pores will not admit oxygen to the central cavity of themicrospheres at a sufficient rate to support gross combustion of thecarbon particle catalyst.

The polyethylne glycol, though having a high solubility and selectivityfor SO₂ when used in thin films or in finely divided form, has atendency to become soft and sticky in use when subjected to modest bodyforce pressures. The polyethylene glycol's general lack of structuralintegrity has prevented its use as a selective solvent in large scalecommercial processes for the selective removal of SO₂.

The present invention in which hollow porous microspheres are used toencapsulate the finely divided molecular sieve carbon particle catalystor the polyethylene glycol selective solvent uncouples the requirementof selective catalytic activity of the carbon catalyst and the selectivesolubility of the polyethylene glycol from the requirements of highmechanical strength and structural integrity.

Encapsulation of Carbon Particles

Hollow porous alumina particle microspheres are prepared and have a 2000to 4000 microns diameter, a 60 to 80 microns wall thickness, a 25 to 35%porosity (in the walls) and macro pores 60 to 80 macrons in size. Themacro pores are selected to be about the same size as the thickness ofthe walls of the microspheres. The microsphere pores in the walls of themicrospheres are about 1 to 3 microns in size.

A batch of the hollow porous microspheres are filled with a conventionalcarbon molecular sieve precursor material. The hollow microspherescontaining the precursor material are then heated in a manner known inthe art to convert the precursor material to carbon molecular sievecatalyst. The carbon particles are examined and are found to have acarbon particle pore size of 4 to 9 angstroms, with a narrow pore sizedistribution. Alternatively, the carbon molecular sieve catalyst can beformed, a slurry of the carbon catalyst made and the microspheres filledthrough the macro pores with the carbon molecular sieve catalyst. Themicrospheres are then treated to remove the carrier from the slurry.

It is found that the finely divided carbon particles do not come outthrough the microsphere pores or macro pores entrance means because theparticles have a small affinity for each other and form looseagglomerates of carbon particles. The loose agglomerates are not subjectto stresses due to their neighbors because they are confined within themicrosphere central cavity. These loose agglomerates can reach a size of100 to 200 microns which also prevents them from coming out through themacro pores of the microspheres.

The method of making finely divided molecular sieve carbon particlecatalyst is well known in the art. The carbon molecular sieves can beprepared by the decomposition of a wide variety of starting materials,including pitch and saran. The molecular sieve carbon structure obtainedis dictated by the controlled cracking and controlled partialgasification of the hydrocarbons contained within the hollowmicrospheres. A discussion of how the molecular sieve carbon particlecatalyst are made is contained in D. L. Trimm, Methods of Preparation ofCarbon Molecular Sieves, Carbon No. 15, 273 (1977).

Since the molecular sieve carbon particles are formed by decompositionof a hydrocarbon, e.g. pitch, to essentially carbon, the carbonparticles remaining in the central cavity after decomposition willusually fill only about one third to one half of the central cavity.Additional filling of the central cavity can be accomplished byrepeating the cycle.

The hollow microspheres, partially filled with carbon catalyst, can bestacked in a tower in the form of a fixed or moving bed, asschematically illustrated in FIG. 9 of the drawings. The carbon catalystwithin the hollow microspheres can form a loose bed. "Ebulliation" canbe practiced to actually cause a stirring of the loose bed of carbonparticles inside of each microsphere. The diameter and densities of themicrospheres and the reactant fluid stream velocities can be adjustedsuch that the microspheres are almost floating in an upwardly movingreactant fluid stream. This can cause a jiggling which would reduce thepath length of diffusion of a reactant into and out of contact with thecatalyst in the central cavity of the microsphere.

Encapsulation of Polyethylene Glycol

The hollow porous microspheres having macro pores are made from analumina dispersed particle composition in accordance with the methoddescribed in applicant's copending application Ser. No. 639,126. Themicrospheres are 2000 to 4000 microns in diameter and 60 to 80 micronswall thickness. The microspheres are substantially uniform in diameterand substantially uniform in wall thickness and porosity. Themicrospheres have a 25-30% porosity and uniform distribution ofinterconnecting voids, are rigid and have relatively high strength. Themicrosphere pore openings are 1 to 3 microns. The microspheres have aplurality of macro pores 80 to 100 microns in diameter.

In order to increase the absorption capacity of the microspheres forSO₂, the microspheres are treated with an alumina sol to fill the hollowcentral cavity of the microspheres with a porous alumina support. Thehollow porous microspheres containing the alumina support are thenimpregnated with a composition to deposit on the microsphere and aluminasupport an immobilized liquid membrane absorbent that is selective toSO₂. The hollow porous microspheres and contained alumina support areused as a substrate for the immobilized liquid membrane absorbent.

The alumina support is prepared by contacting and impregnating thehollow porous microspheres with an aqueous alumina sol dispersioncontaining an about 25 weight percent alumina particles, e.g. 12 to 17volume percent of the sol dispersion. The size of the alumina particlesin the sol dispersion are 0.05 to 0.1 microns. The hollow porousmicrospheres are placed on a porous bed and the alumina sol dispersionis applied to the microspheres. A suction is applied under the bed todraw the alumina sol dispersion into the single central cavity of themicrospheres and to fill the microspheres. The microspheres are dried atabout 65°-100° F. and then washed to remove excess alumina soldispersion. The microspheres containing the dried alumina sol are heatedto a temperature of 260° C. to 900° C. to sinter the alumina solparticles. The alumina sol particles on heating sinter together at theirpoints of contact to form a porous lattice work of alumina particles.The porous lattice work of alumina sol particles form in the singlecentral cavity and in the interconnecting voids and bridging themicrosphere pores in the microsphere walls. The macro pores that are 80to 100 microns in diameter remain open. The porous lattice work ofalumina particles made from the alumina sol dispersion comprise about80% void content and has a pore size of up to 200 microns. The pore sizemeasured is that between clusters of adjacent alumina particles in thelattice work formed by the alumina sol dispersion. The alumina particlesforming the lattice work is now ready for impregnation and coating withan immobilized liquid absorbent. If desired, the microspheres may besubjected to vibration during drying to partially break-up the aluminasupport lattice work. The lattice work can be broken up into aluminaparticle clusters 50 to 200 microns in size with a correspondingreduction pore diffusion resistance.

An immobilized liquid selective polyethylene glycol absorbent membranecoating for the hollow porous microspheres and alumina lattice worksupport contained in the single central cavity of microspheres can beprepared by generally following the procedure described in the W. J.Ward III and C. K. Neulander, Final Report Contract PH-36-68-76, GeneralElectric Research and Development Center, Scenectady, N.Y., March 1970.

To immobilize a liquid solvent thickening agents such as hydroxyethylcellulose, hydroxymethyl cellulose and finely divided silica or aluminaparticles and/or mixtures thereof can be used. To inhibit oxydation ofthe polyethylene glycol an anti-oxidant can be added, e.g. Ionox-330available from Shell Chemical Co. Suitable polyethylene glycol materialswhich exhibit a high selectivity and high solvent capacity for SO₂ areCarbowax 600 and Carbowax 4000 available from Union Carbide Company.

The hollow microspheres are treated with a mixture comprisingpolyethylene glycol, thickening agents and an anti-oxidant. The mixtureis prepared by dissolving about 6 grams of Carbowax (PEG) 4000 in 80 ml.of water, dispersing about 1.2 grams of Cabosil HS-5, a fine grade ofsilica marketed by Cabot Corporation, in 50 ml water and blending theCarbowax solution with the Cabosil dispersion. About one gram ofCellosize (HEC) QP-100M, marketed by Union Carbide Company, is dissolvedin 200 ml. of water and blended into the polyethylene glycol and silicamixture. Optionally about 0.1 to 0.3% Ionox-330 anti-oxidant, based onweight of PEG is added to the mixture. The resulting mixture containsabout 1.8% PEG, 0.35% silica and 0.3% HEC.

A batch of the hollow porous microspheres containing the alumina supportare placed in a thin layer on a bed. The microspheres are sprayed to thepoint of saturation with the above prepared polyethylene glycol mixture.The spraying step is repeated until the microspheres are substantiallyfilled with polyethylene glycol mixture. Alternatively, the microspherescan be immersed in a container containing the polyethylene glycolmixture and if necessary pressure applied to the mixture to assistfilling the microspheres with the mixture.

The microspheres filled with the polyethylne glycol mixtures areseparated and dried to remove water.

The dried microspheres have coated on the inner and outer microspherewall surfaces and have coated on the alumina support lattice workcontained in the single central cavity of the microsphere a thinpolyethylene glycol immobilized liquid membrane about 2 to 10 micronsthick. The macro pores remain open to allow access of the SO₂ gas to beabsorbed to the polyethylene glycol membrane coated on the aluminasupport in the microsphere. If desired the thickness of the polyethyleneglycol membrane coating can be increased by repeating the coating cycle.

The encapsulation of the polyethylene glycol absorbent in the hollowmicrospheres prevents it, during the SO₂ absorption process cycles fromfusing together into large masses.

SO₂ Separation Process.

The stack gas from a coal fired electric power generation plant istreated in accordance with the present invention to remove and recoverSO₂ and to convert nitrogen oxides to nitrogen. The conversion of thenitrogen oxides to nitrogen is considered to be of particular importancein view of recent concern that nitrogen oxides may be a significantfactor in deforestation. The stack gas at a temperature of about 200° F.(93.3° C.) and containing about 0.2% SO₂ by volume is contacted up flowthrough a moving bed reactor containing the hollow porous microspherescatalyst. The hollow porous microspheres contain finely dividedmolecular sieve carbon particle catalyst. The hollow microspheres incontact with stack gas are circulated at a rate of approximately one totwo pounds of the carbon molecular sieve catalyst per minute per MW_(e)per percent sulfur in the coal.

The catalytic reaction for the conversion of SO₂ in the stack gas to H₂SO₄ is: 2SO₂ +O₂ +2H₂ O→2H₂ SO₄.

The H₂ SO₄ and part of the CO₂ in the stack gas are adsorbed by thefinely divided carbon catalyst.

A catalytic reaction for the conversion of nitrogen oxides (NO_(x)) inthe stack gas to nitrogen is: 2CO+2NO→N₂ +2CO₂. The following reactionmay also occur: C+CO₂ +2NO→2CO₂ +N₂.

As mentioned above, the H₂ SO₄ and some CO₂ are adsorbed by the carbonmolecular sieve catalyst. The effluent gas is essentially free of SO₂and NO_(x) and contains primarily CO₂, N₂, H₂ O and O₂ all of which arenon polluting.

The microspheres containing the carbon molecular sieves and adsorbed H₂SO₄ and CO₂ are conveyed to a regenerator vessel in which they aredirectly contacted with a moving bed of hot sand in a manner similar tothat used in the existing "char" process. The hot sand in direct contactwith the microspheres heats the carbon molecular sieves to a temperatureof about 1200° F. (648.8° C.) and converts the adsorbed H₂ SO₄ to SO₂and H₂ O which are desorbed from the molecular sieve carbon catalysttogether with the adsorbed CO₂.

After the carbon catalyst regeneration step the microspheres are cooledto a temperature of about 200° F. (93.3° C.) and are recycled to thecatalytic conversion and adsorption step.

A gas stream comprising about 50% by volume SO₂, 25%CO₂ and 25% H₂ O isoff gassed from the regenerator vessel. The gas stream is cooled to atemperature of about 180° F. (82.3° C.) and compressed to 100 psia. TheH₂ O condenses and is removed and the gas stream containing SO₂ and CO₂is contacted in an up flow adsorption tower with a fixed stacked bed ofthe hollow microspheres containing a thin coating of polyethyleneglycol.

The polyethylene glycol coating exhibits about 35/1 selectivity to SO₂over CO₂. The non adsorbed CO₂ and any remaining H₂ O are exhausted tothe atmosphere.

The adsorption tower is cooled to 80° F. (26.7° C.) and the pressure isreduced to about 30 psia (atmospheric) and the SO₂ dissolved in thepolyethylene glycol comes out of solution, i.e. is desorbed asessentially pure SO₂.

The desorbed SO₂ is compressed to liquify the SO₂ to obtain liquid SO₂product.

EXAMPLE 6

The microsphere catalyst can be treated as described below to obtainmicrosphere catalyst with an inorganic immobilizing membrane ofcontrolled micro pore size.

Microsphere catalyst can have microsphere pores of, for example, 1 to 3microns and macro pores of, for example, 60 to 80 microns in diameter.

The microspheres are collected and are contacted with a stable 50 weightpercent colloidal particle size silica sol dispersion in water. Thesilica particles are about 0.05 to 0.1 microns in size and compriseabout 25 to 35 volume percent of the sol. A positive pressure is appliedabove the liquid level of the silica sol to force the silica sol intothe interconnecting voids in the walls of the hollow porous microspheresto form a layer of sol dispersion to a depth of about one fourth to onethird of the thickness of the microsphere walls (see FIG. 6), e.g. 15 to25 microns.

The microspheres are then cleaned, dried and heated to a temperature ofabout 1000° to 1200° C., i.e., below the melting temperature of thesilica particles, for sufficient time to sinter the silica particles andto remove the water from the silica particles. The sintered silicaparticles form a latticework of particles in the interconnecting voidsin the microsphere walls to the depth the sol penetrates into themicrospheres' walls. The removal of the continuous liquid phase and thefiring and sintering of the sol dispersion results in a slight shrinkagein the thickness of the layer of the sol dispersion in the microspheres'walls.

The silica particles at the points at which they are in contact with thealumina particles that form the surfaces of the interconnecting voidsare partially dissolved into or sintered to the silica particles.

The sintered silica particles comprise a strong lattice work of poroussilica particles with pores of a controlled about 0.10 to 0.50 micronsize, i.e., with micro pores. Particles of colloidal size, other thansilica particles, for example alumina particles can be used in themanner described to form the micro pores.

EXAMPLE 7

The present invention can be used to accomplish a selective separationof a particular constituent of a reactant stream, either liquid or gas,in such a manner as to have only the selected constituent reach aspecific catalyst contained within the central cavity of the hollowporous microspheres of the present invention. This is accomplished byimpregnating and/or filling the microspheres with the desired catalystthen coating the microsphere with an inorganic selective membrane.

A desired catalyst is first placed in the central cavity of themicrospheres and/or impregnated in the interconnecting voids and on theinner wall surfaces of the walls of the microspheres.

The microspheres can contain microsphere pores of about 1 to 3 micronsin diameter. In situations where the microsphere pores are much larger atemporary substrate, e.g. of an organic polymer material can be providedon which to deposit the inorganic selective membrane precursor material.The temporary organic substrate is removed on heating to sinter theinorganic membrane.

Hollow porous alumina particle microspheres are prepared having a 2500to 3000 micron diameter, a 40 to 60 micron wall thickness and a 1 to 3micron microsphere pore size. The microspheres are treated to fill thesingle central cavities with a desired catalyst.

The microspheres are then treated to deposit on their outer wallsurfaces a thin inorganic selective membrane. An inorganic selectivealumina membrane having uniform pore size of about 2.5 to 5.0 nm (0.0025to 0.0050 microns) can be deposited on the microsphere walls. Themembrane is applied by spray coating the microspheres with an aqueousboehmite (gamma-A100H) sol dispersion. The boehmite sol is preparedgenerally following the procedure described in Leenaars et al, Journalof materials Science 19, pages 1077-1088 (1984) as briefly discussedbelow.

The boehmite (gamma-A100H) sol is prepared by adding aluminum secondarybutoxide to water which is heated to a temperature above 80° C., e.g.about 85° C. and stirred. Two liters of water are used per mole ofbutoxide. The solution is kept at about 90° C. and about 1/2 to 1 hourafter addition of the butoxide, 0.07 mole HNO₃ per mole alkoxide isadded to peptize the sol particles. The sol is kept boiling in the openreactor for 2-3 hours to evaporate most of the butanol and issubsequently kept at 90°-100° C. for about 16 hours under refluxconditions.

The sols, as mentioned above, are then sprayed onto the microspheres.The sold fills the outer pore openings of the microspheres and theinterconnecting voids of the microspheres to deposit a layer of sol10-20 microns thick.

The microspheres are then heated to dry the sol and convert the sol to agel. The microspheres are further heated and the temperature graduallyincreased to 400°-900° C. to sinter the alumina particles in the gel.The deposited layer shrinks slightly during sintering due to the removalof water to a thickness of about 6-12 microns. The sintered alumina filmcan have a model pore size of about 2.5-5.0 nm and a porosity of about40 to 50%. The thin alumina film is supported by the surfaces of theinterconnecting voids in the microsphere walls. The micropores of2.5-5.0 nm are examined and are found to have a narrow sizedistribution.

The microsphere catalyst can be used to carryout processes in whichselected reactants having molecular size less than about 2.5 to 5.0 nmare allowed to enter the microsphere central cavity, contact thecatalyst and to react. Reactant constituents having a molecular sizelarger than about 2.5 to 5 nm are excluded from entering the microspherecentral cavity and are prevented from contacting the catalyst.

A microsphere catalyst containing deposited on its outer wall surface aninorganic selected membrane can thus be used to combine in a singleprocess step the selection of a specific constituent of a reactantstream and the catalytic reaction of the selected constituent. Becausethe selective membrane is inorganic the microsphere catalyst can be usedat relatively high temperatures under relatively severe reaction mediumconditions.

EXAMPLE 8

The microsphere catalysts prepared in accordance with the presentinvention can be treated to impregnate the porous microsphere wall withan organic selective semipermeable membrane. The organic selectivesemipermeable membrane is used in applications in which the catalyticreaction is carried out at a relatively low temperature, e.g. below 300°C. and preferrably below 200° C.

The use of the organic selective semipermeable membrane allows aselective separation process to be combined with a catalytic reactionprocess.

The hollow porous microspheres are treated to impregnate the microspherewith a desired catalyst or the microspheres are treated to fill thecentral cavity of the microspheres with the desired catalyst.

A microsphere, e.g. having a diameter of about 2500 microns and a wallthickness of about 40 to 50 microns with entrance means (macro pores) ofabout 40 to 50 microns in diameter extending through the wall, and anaverage microsphere pore diameter of about 1-3 microns is used.

Following the teachings of applicant's copending application, Ser. No.657,090, filed Oct. 3, 1984 an organic selective semipermeable membraneis applied to the porous wall of the microsphere catalyst.

After the impregnation or filling the microspheres with catalyst andafter activation of the catalyst the microspheres are cleaned and dried.The microspheres are then transferred to a beaker containing 150 ml ofsolution comprising one part of a 2% 2(cyclohexylamino) ethane sulfonicacid solution in 0.5% NaCl (isotonic, pH=8.2) diluted with 20 parts 1%CaCl₂. After a 3 minute immersion, the microspheres are washed twice in1% CaCl₂.

The microspheres are then transferred to a solution comprising 1/80 ofone percent polylysine (average MW 35,000 AMU) in an aqueous salinesolution. After 3 minutes, the polylysine solution is decanted. Themicrospheres are then washed with 1% CaCl₂, and then suspended for 3minutes in a solution of polyethyleneimine (MW 40,000-60,000) producedby diluting a stock 3.0% polyethyleneimine solution in morpholinopropane sulfonic acid buffer (0.2M, pH=6) with sufficient 1% CaCl₂ toresult in a final polymer concentration of 0.10%. The resultingmicrospheres have permanent semipermeable membranes extending across themacro pores and microsphere pores at the exterior wall surface. Theresulting microsphere catalyst are then washed twice with 1% CaCl₂,twice with an aqueous saline solution, and mixed with 100 ml of a 0.12percent alginic acid solution. The microsphere catalysts resist clumpingand contain an active catalyst.

Under microscope examination, a cross-section of the microsphere wallsare found to have an appearance illustrated in FIGS. 4 and 7 of thedrawings. The microspheres comprise an ultrathin membrane 44 (FIG. 4)and 50 (FIG. 7) extending within and across the macro pores (FIG. 4) andmicrosphere pores (FIG. 7) near the periphery of the microsphere walls.The catalyst contained within the microspheres are isolated fromchemicals having a larger molecular size than the size that can permeatethrough the organic selective semi-permeable membrane. However, reactantmolecules having a molecular size small enough to permeate through themembrane can transverse membrane 44 into central cavity 50. This allowsreactants to reach the catalyst contained in the microsphere and allowsproducts to be removed from the single central cavity into thesurrounding reaction medium.

The organic selective semipermeable membrane can be made from otherconventional organic membrane materials and the particular material isselected to have the desired permeation or diffusion properties.

The catalyst selected to be encapsulated can be any of the conventionalcatalyst to carryout a desired catalyst reaction. Obviously the organicsemipermeable membrane must allow permeation or diffusion of thereactant to reach the catalyst and the catalyst reaction must be carriedout at temperatures sufficiently low such that the organic selectivesemipermeable membrane is not altered or damaged during the catalystreaction.

The rigid walls of the microspheres provide all the required structuralsupport for and protect the semipermeable membrane and catalyst fromshearing forces and mechanical damage. Therefore, the semipermeablemembranes can be substantially thinner than in conventionalsemipermeable membrane systems wherein the membranes also provide thestructural support. This allows the microsphere catalyst to be used atmuch larger packing densities, in long columns, and in fixed, moving bedor fluidized bed processes.

UTILITY

The catalysts that are used are those that are conventionally used inthe industry and can be added to the microspheres or microspheres andcatalyst support in the form of solutions, sols, slurries or melts. Thecatalyst can be added to the microspheres or microspheres and support bycoating the outer wall surface of the microspheres, impregnating theinterconnecting voids in the walls of the microspheres, coating theinterior wall surfaces of the microspheres and can be used to fill orpartially fill the single central cavity of the microspheres. Thecatalysts or catalyst supports can be formed in situ in the walls or inthe single central cavity. The catalysts can be activated or calcined inthe manner conventional in the art.

The inorganic selective membranes or the organic selective semipermeablemembranes that can be used to coat or impregnate the walls of themicrospheres are those conventionally used in the art to carryoutselective separations. The distinction, however, is that the membranescan be used in thicknesses of about 0.1 to 20 microns, preferrably 0.5to 5.0 microns, since the strength is supplied by the rigid wall of thehollow porous microsphere.

The microsphere catalyst of the present invention can be used tocarryout a wide variety of catalytic reactions.

These and other uses of the present invention will become apparent tothose skilled in the art from the foregoing description and the appendedclaims.

It will be understood that various changes and modifications may be madein the invention, and that the scope thereof is not to be limited exceptas set forth in the following claims.

I claim:
 1. A process for carrying out a catalytic reaction whichcomprises contacting hollow porous microsphere catalyst with a reactionmedium under conditions such that at least one constituent in thereaction medium is brought into contact with the catalyst for a periodof time sufficient for said constituent to undergo a chemical change,said microsphere catalyst comprising hollow porous microspheres having asubstantially uniform diameter of 200 to 10,000 microns and asubstantially uniform wall thickness of 1.0 to 1000 microns, the wallsof said microspheres comprise sintered together particles which defineinterconnecting voids within the walls and a single central cavity inthe interior of the microspheres and inner and outer microsphere wallsurfaces, said interconnecting voids are continuous and extend from theouter wall surface to the inner wall surface, said walls havesubstantially uniform void content and said interconnecting voids aresubstantially uniformly distributed in the walls of the hollowmicrospheres, said walls include entrance means through which a reactantcan be introduced into the interconnecting voids and into the singlecentral cavity of the microspheres, said microspheres have catalyst onthe particles forming the walls or have catalyst contained within thesingle central cavity or have catalyst on the particles forming thewalls and have catalyst contained within the single central cavity, andthe walls of said microspheres are free of latent solid or liquidblowing gas materials and are substantially free of relatively thinnedwall portions or sections and bubbles.
 2. The process of claim 1 whereinthe catalyst is on the particles forming the interconnecting voids andon the particles forming the inner wall surface of the microspherewalls.
 3. The process of claim 1 wherein the catalyst is containedwithin the single central cavity in the interior of the microspheres. 4.The process of claim 1 wherein the microsphere catalysts havedistributed in the walls macro pores which are 1 to 1000 microns in sizeand which extend through the microsphere walls.
 5. The process of claim1 wherein the microsphere catalysts are contained as a stacked bed in areactor.
 6. The process of claim 1 wherein the microsphere catalysts arecontained as a moving bed in a reactor.
 7. The process of claim 1wherein the microsphere catalysts are contained as a fluidized bed in areactor.
 8. The process of claim 1 wherein the sintered particlesforming the walls of the microspheres comprise ceramic particles.
 9. Theprocess of claim 1 wherein the sintered particles forming the walls ofthe microspheres comprise alumina particles.
 10. The process of claim 3wherein the microsphere catalysts contain in the microsphere entrancemeans an inorganic selective membrane.
 11. The process of claim 3wherein the microsphere catalysts contain in the microsphere entrancemeans an organic selective semipermeable membrane.
 12. The process ofclaim 1 wherein the microsphere catalysts contain catalyst within thesingle central cavity and the catalyst is in the form selected from thegroup of finely divided solid particles, finely divided resin particlesand a gel.
 13. A method for controlling CO and hydrocarbon constituentsin an auto exhaust which comprises placing in a container a bed of autoemission control microsphere catalyst comprising hollow porousmicrospheres of substantially uniform diameter of 500 to 6000 micronsand of substantially uniform wall thickness of 5.0 to 400 microns, thewalls of said microspheres comprise sintered together alumina particleswhich define interconnecting voids within the walls and a single centralcavity in the interior of the microspheres and inner and outermicrosphere wall surfaces, said interconnecting voids are continuous andextend from the outer wall surface to the inner wall surface, said wallshave substantially uniform void content and said interconnecting voidsare substantially uniformly distributed in the walls of the hollowmicrospheres, said microspheres have a catalyst selected from the groupconsisting of platinum, palladium and rhodium and mixtures thereofcoated or impregnated on the inner and outer wall surfaces of themicrospheres and on the particles forming the interconnecting voids inthe wall of the microspheres, and the walls of said microspheres arefree of latent solid or liquid blowing gas materials and aresubstantially free of relatively thinned wall portions or sections andbubbles, installing the container in an engine exhaust line andcontacting the engine exhaust with the microsphere catalysts to convertthe CO to CO₂ and hydrocarbons to CO₂ and H₂ O and to thereby reduce theconcentration of CO and hydrocarbons in the exhaust.
 14. The method ofclaim 13 for controlling CO and hydrocarbon constituents in an autoexhaust wherein the engine exhaust is contacted with the microspherecatalyst at a temperature of about 200 to 300° C.
 15. The method ofclaim 14 wherein the CO and hydrocarbon constituents of the exhaust gasare reduced by at least 30 to 50% by volume.
 16. The method of claim 13wherein the microsphere catalyst have distributed in the walls macropores which are 5 to 400 microns in size and which extend through themicrosphere walls.
 17. A method for reducing the sulfur and nitrogencontent of a hydrocarbon feed containing sulfur or nitrogen whichcomprises contacting a hydrodinitrification and hydrodesulfurizationcatalyst comprising hollow porous microspheres of substantially uniformdiameter of 500 to 6000 microns and of substantially uniform wallthickness of 5.0 to 400 microns, the walls of said microspheres comprisesintered together alumina particles which define interconnecting voidswithin the walls and a single central cavity in the interior of themicrospheres and inner and outer microsphere wall surfaces, saidinterconnecting voids are continuous and extend from the outer wallsurface to the inner wall surface, said walls have substantially uniformvoid content and said interconnecting voids are substantially uniformlydistributed in the walls of the hollow microspheres, said microsphereshave contained within the single central cavity and have within theinterconnecting voids a catalyst selected from the group consisting ofcobalt-molybdenum, nickel-molybdenum and nickel-tungsten and the oxidesand sulfides thereof and mixtures thereof, and the walls of saidmicrospheres are free of latent solid or liquid blowing gas materialsand are substantially free of relatively thinned walls portions orsections and bubbles in a reactor vessel with the hydrocarbon feed andhydrogen and removing sulfur and nitrogen from the hydrocarbon feed. 18.The method of claim 17 wherein the hydrocarbon is contacted with themicrosphere catalyst at a temperature of 250° C. to 450° C., pressuresof 30-200 atmospheres and hydrogen gas rates of 2000 to 12,000 standardcubic feet of hydrogen per barrel of feed.
 19. The method of claim 17wherein hydrodinitrification of the feed is carried out and themicrosphere catalyst comprises a member of the group consisting ofnickel-molybdenum and nickel tungsten and the oxides and sulfidesthereof and mixtures thereof.
 20. The method of claim 17 whereinhydrodesulfurization of the feed is carried out and the microspherecatalyst comprises a member of the group consisting of cobalt-molybdenumand the oxides and sulfides thereof and mixtures thereof.
 21. A methodfor hydrocracking a hydrocarbon feed to obtain hydrocarbons of a lowermolecular weight than said feed hydrocarbons which comprises contactinga hydrocracking catalyst comprising hollow porous microspheres ofsubstantially uniform diameter of 500 to 6000 and of substantiallyuniform wall thickness of 5.0 to 400 microns, the walls of saidmicrospheres comprise sintered together alumina particles which defineinterconnecting voids within the walls and a single central cavity inthe interior of the microspheres and inner and outer microsphere wallsurfaces, said interconnecting voids are continuous and extend from theouter wall surface to the inner wall surface, said walls havesubstantially uniform void content and said interconnecting voids aresubstantially uniformly distributed in the walls of the hollowmicrospheres, said microspheres have contained within the single centralcavity a nickel catalyst and the walls of said microspheres are free oflatent solid or liquid blowing gas materials and are substantially freeof relatively thinned wall portions or sections and bubbles in a reactorvessel with the hydrocarbon feed and hydrogen under hydrocarbon crackingconditions and cracking the hydrocarbon feed to obtain hydrocarbons of alower molecular weight than the feed.
 22. The method of claim 21 whereinthe hydrocarbon is contacted with the microsphere catalyst at atemperature of about 343 to 454° C., pressures of about 500 to 2000 psiaand hydrogen gas rates of about 500 to 15000 standard cubic feet ofhydrogen per barrel of feed.
 23. A catalytic cracking catalystcomprising hollow porous microspheres of substantially uniform diameterof 500 to 6000 microns and of substantially uniform wall thickness of5.0 to 400 microns and having macro pores 5.0 to 400 microns in sizewhich extend through the walls, the walls of said microspheres comprisesintered together alumina particles which define interconnecting voidswithin the walls and a single central cavity in the interior of themicrospheres and inner and outer microsphere wall surfaces, saidinterconnecting voids are continuous and extend from the outer wallsurface to the inner wall surface, said walls have substantially uniformvoid content and said interconnecting voids are substantially uniformlydistributed in the walls of the hollow microspheres, said microsphereshave contained within the single central cavity crystalline zeolitemolecular sieve catalyst, and the walls of said microspheres are free oflatent solid or liquid blowing gas materials and are substantially freeof relatively thinned wall portions of sections and bubbles.
 24. Thecatalytic cracking catalyst of claim 23 wherein the microspheres have adiameter of 2000 to 4000 microns and a wall thickness of 30 to 50microns and the walls contain macro pores about 40-60 microns in sizewhich extend through the walls of the microspheres.
 25. The catalyticcracking catalyst of claim 23 wherein the single central cavity of themicrospheres contains loose agglomerates of 13Y crystalline zeolitemolecular sieve catalyst.
 26. The catalytic cracking catalyst of claim23 wherein the crystalline zeolite molecular sieve catalyst containscation-exchanged rare earth elements of the lanthanum rare earth series.27. The catalytic cracking catalyst of claim 23 wherein the crystalinezeolite molecular sieve catalyst contains a rare earth element selectedfrom the group consisting of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium and gadolinium and mixtures thereof. 28.A method for catalytically cracking a hydrocarbon petroleum fraction toincrease the yield of light cycle oil and gasoline which comprisescontacting a catalytic cracking catalyst comprising hollow porousmicrospheres of substantially uniform diameter of 500 to 6000 micronsand of substantially uniform wall thickness of 5.0 to 400 microns andhaving macro pores 5.0 to 400 microns in size which extend through thewalls, the walls of said microspheres comprise sintered together aluminaparticles which define interconnecting voids within the walls and asingle central cavity in the interior of the microspheres and inner andouter microsphere wall surfaces, said interconnecting voids arecontinuous and extend from the outer wall surface to the inner wallsurface, said walls have substantially uniform void content and saidinterconnecting voids are substantially uniformly distributed in thewalls of the hollow microspheres, said microspheres have containedwithin the single central cavity crystalline zeolite molecular sievecatalyst, and the walls of said microspheres are free of latent solid orliquid blowing gas materials and are substantially free of relativelythinned wall portions or sections and bubbles in a reactor vessel withthe hydrocarbon and catalytically cracking the hydrocarbon.
 29. Themethod of claim 28 wherein the petroleum hydrocarbon feed is contactedwith the microsphere catalyst at temperatures of about 300° to 600° C.in a catalytic reactor and catalytically cracking the hydrocarbons. 30.A microsphere catalyst for removing SO₂ from gases and for convertingNO_(x) in gases to N₂ comprising hollow porous microspheres ofsubstantially uniform diameter of 500 to 6000 microns and ofsubstantially uniform wall thickness of 5.0 to 400 microns, the walls ofsaid microspheres comprise sintered together alumina particles whichdefine interconnecting voids within the walls and a single centralcavity in the interior of the microspheres and inner and outermicrosphere wall surfaces, said interconnecting voids are continuous andextend from the outer wall surface to the inner wall surface, said wallshave substantially uniform void content and said interconnecting voidsare substantially uniformly distributed in the walls of the hollowmicrospheres, said microspheres have contained within the single centralcavity finely divided carbon catalyst particles, and the walls of saidmicrospheres are free of latent solid or liquid blowing gas materialsand are substantially free of relatively thinned wall portions orsections and bubbles.
 31. The microsphere catalyst of claim 30 whereinthe walls of said microspheres contain macro pores 5.0 to 400 microns insize which macro pores extend through the walls of the microspheres. 32.The microsphere catalyst of claim 30 wherein the finely divided carboncatalyst particles comprise molecular sieve carbon in the form of looseagglomerates of carbon particles.
 33. The microsphere catalyst of claim30 wherein the microspheres have a 2000 to 4000 micron diameter, a wallthickness of 60 to 80 microns and macro pores 60 to 80 microns in sizewhich macro pores extend through the walls of the microspheres.
 34. Themicrosphere catalyst of claim 32 wherein molecular sieve carbon catalystis capable of converting SO₂ to H₂ SO₄ and of adsorbing H₂ SO₄.
 35. Amethod of removing SO₂ from gases containing SO₂ which comprisescontacting the microsphere catalysts of claim 30 containing finelydivided carbon catalyst particles in a reactor vessel with said gas,converting SO₂ to H₂ SO₄ and adsorbing H₂ SO₄ on the finely dividedcarbon particles.
 36. A method of converting the NO_(x) content of gasesto N₂ which comprises contacting the microsphere catalysts of claim 33containing finely divided molecular sieve carbon catalyst in a reactorvessel with said catalyst and converting NO_(x) to N₂.
 37. The method ofclaim 35 wherein the contacting step is carried out at a temperature ofabout 200° F.
 38. The method of claim 36 wherein the contacting step iscarried out at a temperature of about 200° F.
 39. A microsphereabsorbent, for selectively removing SO₂ from a gas stream containingSO₂, comprising hollow porous microspheres of substantially uniformdiameter of 500 to 6000 microns and of substantially uniform wallthickness of 5.0 to 400 microns, the walls of said microspheres comprisesintered together alumina particles which define interconnecting voidswithin the walls and a single central cavity in the interior of themicrospheres and inner and outer microsphere wall surfaces, saidinterconnecting voids are continuous and extend from the outer surfaceto the inner wall surface, said walls have substantially uniform voidcontent and said interconnecting voids are substantially uniformlydistributed in the walls of the hollow microspheres, said microsphereshave contained within the single central cavity polyethylene glycolwhich has a high solubility for SO₂ and the walls of said microspheresare free of latent solid or liquid blowing gas materials and aresubstantially free of relatively thinned wall portions or sections andbubbles.
 40. The microsphere adsorbent of claim 39 wherein the walls ofsaid microspheres contain macro pores 5.0 to 400 microns in size whichmacro pores extend through the walls of the microspheres.
 41. Themicrosphere absorbent of claim 39 wherein the polyethylene glycolcomprises polyethylene glycol in the form of an immobilized liquidmembrane coating on the surfaces of the alumina particles forming themicrosphere walls.
 42. The microsphere adsorbent of claim 39 wherein themicrospheres have a 2000 to 4000 micron diameter, a wall thickness of 60to 80 microns and macro pores 60 to 80 microns in size which macro poresextend through the walls of the microspheres.
 43. The microspheresadsorbent of claim 41 wherein the polyethylene glycol is capable ofselectively adsorbing SO₂ from a mixture containing a high concentrationof SO₂ and CO₂.
 44. A method of removing SO₂ from a gas streamcontaining SO₂ which comprises contacting the microsphere absorbent ofclaim 39 containing polyethylene glycol with said gas in an absorptionvessel and selectively absorbing SO₂ in the polyethylene glycol.
 45. Themethod of claim 44 for removing SO₂ from a gas stream containing SO₂which comprises contacting the microsphere absorbent containingpolyethylene glycol in the form of an immobilized liquid membrane saidgas at elevated pressures of about 100 psia and absorbing said SO₂ intosaid polyethylene glycol membrane.
 46. The method of claim 44 whereinthe SO₂ is selectively absorbed from a gas stream containing a highconcentration of SO₂ and CO₂, and the SO₂ is desorbed by reducing thepressure to about 30 psia.
 47. A process for carrying out a catalyticreaction which comprises contacting hollow porous microsphere catalystwith a reaction medium under conditions such that at least oneconstituent in the reaction medium is brought into contact with thecatalyst for a period of time sufficient for said constituent to undergoa chemical change, said microsphere catalyst comprising hollow porousmicrospheres having a substantially uniform diameter of 500 to 6000microns and a substantially uniform wall thickness of 5 to 400 microns,the walls of said microspheres comprise sintered together particleswhich define interconnecting voids within the walls and a single centralcavity in the interior of the microspheres and inner and outermicrosphere wall surfaces, said interconnecting voids are continuous andextend from the outer wall surface to the inner wall surface, said wallshave substantially uniform void content and said interconnecting voidsare substantially uniformly distributed in the walls of the hollowmicrospheres, said walls include entrance means through which a reactantcan be introduced into the interconnecting voids and into the singlecentral cavity of the microspheres, said microspheres have catalyst onthe particles forming the walls or have catalyst contained within thesingle central cavity or have catalyst on the particles forming thewalls and have catalyst contained within the single central cavity, andthe walls of said microspheres are free of latent solid or liquidblowing gas materials and are substantially free of relatively thinnedwall portions or sections and bubbles.
 48. The process of claim 47wherein the walls of said microspheres comprise sintered togetherceramic particles.
 49. The process of claim 47 wherein the walls of saidmicrospheres comprise sintered together alumina particles.
 50. Theprocess of claim 47 wherein the walls of said microspheres comprisesintered together glass particles.
 51. The process of claim 47 whereinthe walls of said microspheres comprise sintered together metalparticles.
 52. The process of claim 47 wherein the walls of saidmicrospheres comprise sintered together metal glass particles.
 53. Theprocess of claim 47 wherein the walls of said microspheres comprisesintered together plastic particles.
 54. The process of claim 47 whereinthe void content of the walls of the microspheres comprises 15 to 35percent by volume of the microsphere walls.
 55. The process of claim 47wherein the microsphere catalyst have distributed in the walls macropores which are 5 to 400 microns in size and which extend through themicrosphere walls.
 56. The process of claim 47 wherein the microspherewalls contain entrance means and there is contained in the entrancemeans an inorganic selective membrane.
 57. The process of claim 47wherein the microsphere walls contain entrance means and there iscontained in the entrance means an organic selective semipermeablemembrane.